Sound Practices Mailing List Files - Volume 2
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From: Dan Marshall <mdaniel7@uswest.net>
Subject: [JN] 200CD Transformer Evaluation
Date: Fri, 21 Jul 2000 14:35:06 -0700
Source: Sound Digest Archive v02.n608
Hi All,
I received the 200CD output transformer set from Rick Francis and had a
look at them. They consist of a small round, phenolic transformer which
is good only above 5 kHz, so is not of much interest in the audio band,
unless one wishes to triamp.
The low frequency transformer is an altogether different matter, a
rather beefy unit, about the size of the opts in the Heath EA-2
amplifiers except with about 2/3 the core thickness. They show quite a
lot of promise as interstage transformers for tube amplifers.
Unfortunately, they are open-frame units and would require end bells, or
potting for a nice appearance.
They are PP cathode driven in the 200CD oscillator, with series
resistors (a couple hundred ohms) and a 600 ohm Tee attenuator on the
output. They have three windings, essentially 1:1:1 turns ratio. Two
of the windings are used for the PP primary in the 200 CD. The winding
dc resistances measure from about 108 ohms to 137 ohms. After
experimenting around it was determined that for an IT it seems to
perform better if the secondary winding is used as the primary with the
two primaries in series for the secondary. The original primaries are
labeled as terminals 1&2 and 3&4, and the secondary as 5&6. Two
configurations were optimized, PP and SE. The input was into terminals
5&6 with 6 grounded in all cases.
In SE connection, it was found that it performs best with the two (now
secondary) windings in series with terminals 1&4 joined, terminal 2 to
ground with the output taken from terminal 3. Secondary loading, if
used, seems to work best across both windings rather than split across
the two halves. This is the opposite of most of the cheapie ITs. It is
in general less tempermental and better performing than the cheapie ITs.
The value of primary driving impedance is rather critical to achieve
flat response to 20 kHz w/o overshoot or ringing, and it is possible to
achieve this without secondary loading. The optimum source resistance
was found to be 1.3k in series with the 600 ohm generator output
impedance for a total of 1.9k. This gives just a bit of overshoot which
settles right down. With this primary driving resistance it has flat
frequency response to 20 kHz, where it starts a very gentle and
well-mannered rolloff. A bit less overshoot is attained with slightly
greater driving impedance, but the response will be off about 1/2 to 1
dB at 20 kHz. If a bit lower source impedance is used, it needs a bit
of secondary damping (to attain good square wave response w/o ringing),
to which it responds well. This will extend the high frequency response
a bit farther. It may be a bit tricky to get a driver tube with optimum
rp, so it would seem reasonable to drive it with a tube that exhibits a
bit less than 1.9k rp, then tweak the secondary loading a bit for best
squarewave response. It is very well mannered and it doesn't take much
secondary loading to tame it quite nicely. If give or take a dB at 20
kHz doesn't upset you, then a driver tube exhibiting an rp in the range
of 1.8 k to 2 k should do quite nicely. If a purist, then tweak it a
bit.
It doesn't perform well with the two secondaries in parallel and it does
not work well in the cap-bridged mode, as the winding ratio is not
exactly 1:1 from the primary to one secondary, close, but not exact.
For PP use, use the same primary connection, join 1&4 for the secondary
ct and connect to ground, or bias supply, and take the outputs from
terminals 2&3. Separately, these outputs exhibit some ringing, no
matter how you terminate the primary, but when they are summed on the
scope, the ringing pretty well cancels out. It is not a large ring, so
this ought to be OK. A driving impedance of 2k total is optimum. The
summed outputs exhibit a small amount of ringing, but a very small
amount. There is a rather narrow pre shoot spike on the trailing edge,
but it is up fairly high in frequency and is not likely to be excited by
anything in the audio band. In the PP mode it is flat to 30 kHz. One
half of a 6BL7 ought to be a good driver tube.
In either configuration, the low frequency response is quite excellent,
being flat on down to well below 10 Hz when driven by a 2k source
impedance. In the SE configuration (~1:2), I measured about 110 volts
PP at 10 Hz with no evidence of core distortion. It was being driven by
an operable 200CD at its maximum output voltage. So, at 20 Hz, you
should have the capability of driving most lo-mu triodes. I did not
examine its ability to handle dc current. It does not have an air gap
and the core is varnished, so I didn't try to take it apart, though this
might be possible. It may handle some dc. Perhaps I will look at this
later.
All in all, I was quite pleased with its performance and would not
hesitate to incorporate it into an amplifier design. Examining the
200CD transformers for their suitability as interstage transformers was
a good idea Rick.
Dan Marshall
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From: =?iso-8859-1?Q?Tom_Andr=E9_Hansen?= <fishfish@yifan.net>
Subject: [JN] 205 ...
Date: Sun, 11 Mar 2001 03:06:07 +0100
Source: Sound Digest Archive v02.n830
Intrigued by their shape; I might go about something I seldom do. Buy stuff
because of their look, and not their performance.
New Sensor have the (in)famous Allmusic tubes. I've read much crap, but some
like them. It's mostly that cool looking 300B I've found thoughts on. Does
anybody on this list have something to say about Allmusic?
Why I wrote (that might be a little woolly yet).
The tennis ball 205D I know something about, but the 101D, or 102D? Haven't
found much about those two (also two funky looking creatures as far as I
have understood).
So info on 101D/102D, and Allmusic in general, would be greatly appreciated.
If I'm really lucky I person who use the 101D/102D/205D will answer this :)
PS! I do of course hope that these tubes perform very well -- if I am to buy
some Wimbledon globes.
- --
Tom André Hansen
http://cgiperlsite.virtualave.net
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From: TubeGarden@aol.com
Subject: Re: [JN] 205 ...
Date: Sun, 11 Mar 2001 12:45:31 EST
Source: Sound Digest Archive v02.n830
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Content-Transfer-Encoding: 7bit
dunno
316A is a fine sounding tennis ball, and cheap, to boot :)
Ears!
Al B^}
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<HTML><FONT FACE=arial,helvetica><BODY BGCOLOR="#ffffff"><FONT SIZE=2>dunno
<BR>
<BR>316A is a fine sounding tennis ball, and cheap, to boot :)
<BR>
<BR>Ears!
<BR>
<BR>Al B^}
<BR>
<BR></FONT></HTML>
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From: =?iso-8859-1?Q?Tom_Andr=E9_Hansen?= <fishfish@yifan.net>
Subject: Re: [JN] 205 ...
Date: Mon, 12 Mar 2001 00:54:58 +0100
Source: Sound Digest Archive v02.n830
316A? Why not ... I was thinking about using the 205D as a output tube, but
I changed my mind. Though looking at the data of the 102D tube -- that might
be an interesting tube to play with (preamp maybe).
The 316A sure is a sturdy tube. Found this while looking for info on it
"Bryant: When did you first learn the then-secret subject, what we call
radar?
Pound: On the occasion of my visit in 1940. They had an operating radar that
they had developed on their own initiative.
Bryant: Aimed toward a Navy application?
Pound: Well, no. It was for research. Well, it was supposedly a ground-based
system or a ship based. It used two tapered horns with apertures about 4 x 6
feet that were mounted on a big rotatable platform that they had built up on
the roof. I'm not sure if that was finished when I first came, but we had it
running the next year. It was a 50 cm system, and it used a Western Electric
316A doorknob tube. They hit it with 2500 volts pulses. It was a 300 volt
tube. The input pulse power was two kilowatts."
Wow :)
- --
Tom André Hansen
http://cgiperlsite.virtualave.net
=========================================================================
From: Adnan Arduman <adnana@turk.net>
Subject: [JN] 20 Audiophiles and Their Sanctuaries
Date: Mon, 26 Apr 1999 10:40:57 +0200
Source: Sound Digest Archive v02.n131
Hi All,
If you wish to have a look, there are now 20 entries in "My Friends'
Systems" section of my web site: http://www.arduman.com/aa
Other updated sections are "Links" and "Updated CD's".
Any views are appreciated.
Many thanks in anticipation.
Adnan Arduman
visit my personal "NUANCE & FLUENCE" web site:
http://www.arduman.com/aa
tel: +90-216-310 44 70 (w)
fax: +90-216-343 42 01
e-mail: adnana@turk.net
=========================================================================
From: Adnan Arduman <adnana@turk.net>
Subject: Re: [JN] 20 Audiophiles and Their Sanctuaries
Date: Tue, 27 Apr 1999 11:31:54 +0200
Source: Sound Digest Archive v02.n132
Hi Bart,
Thanks for the suggestions which are noted.
In fact the speaker I'm looking for is for my future project (which is
going to be an integrated 300B SE). Therefore I have to look for something
more efficient than the Response 3.5's (89 dB/m/W). I do not have any bias
for any type of speakers but I'm just very curious to hear a Lowther based
one as I could not succeed to acheive that for such a long time. Maybe I'll
hate them (I hope not!) at the end of the day but I still wish to hear at
least one. I hope Tom Ronan will help me in this when I'll be in Chicago at
mid May. I promise to write back what I think.
Thanks again,
Adnan
>If you are used to the Responses, I wouldn't hold out too much hope for a
>Lowther full-range. Maybe as a mid-range horn augmented by a sub and
>possibly also a super-tweeter.
>
>Maybe a TAD horn plus a JBL in an Onken enclosure??
>
>I am using Hyperwhamodynes and also Tannoy 15 inch. Neither is totally
>satisfactory but something along the 'whamo's idea (big TQWP with 4 drivers
>+ tweeter) with better drivers might just do it.
>
>With the 845's you only need 92 - 96 db efficiency.
>
>Cheers,
>
>Bart
visit my personal "NUANCE & FLUENCE" web site:
http://www.arduman.com/aa
tel: +90-216-310 44 70 (w)
fax: +90-216-343 42 01
e-mail: adnana@turk.net
=========================================================================
From: Adnan Arduman <adnana@turk.net>
Subject: Re: [JN] 20 Audiophiles and Their Sanctuaries
Date: Tue, 27 Apr 1999 11:36:57 +0200
Source: Sound Digest Archive v02.n132
Lance,
>For some strange reason, I wasn't able to access your site tonight, but
>I've been following you work on and off since January. I think it's
>excellent and I've recommended that we do something similar with our Web
>page. We're in the process of collecting photos/write-ups on members'
>systems to get things going.
Many thanks for your encouraging comments. I hope you will try to access
one more time today.
>I'll keep you informed of our progress.
I'll be very pleased if you do.
Sincerely,
Adnan
visit my personal "NUANCE & FLUENCE" web site:
http://www.arduman.com/aa
tel: +90-216-310 44 70 (w)
fax: +90-216-343 42 01
e-mail: adnana@turk.net
=========================================================================
From: Adnan Arduman <adnana@turk.net>
Subject: Re: [JN] 20 Audiophiles and Their Sanctuaries -Reply
Date: Tue, 27 Apr 1999 18:34:54 +0200
Source: Sound Digest Archive v02.n133
Hi Ralph,
Thanks for your input. As I am a total ignorant on the subject of Lowthers,
I'm copying this e-mail to Tom Ronan. I hope he will have the setup you
mention. I was also planning to write to Tom directly and I would like to
ask him to accept my apologies for such an indirect first contact.
Your 2 cents are on the way.
Adnan
>Hi Adnan,
>
>You said :
>
>>In fact the speaker I'm looking for is for my future project (which is
>>going to be an integrated 300B SE). Therefore I have to look for something
>>more efficient than the Response 3.5's (89 dB/m/W). I do not have any bias
>>for any type of speakers but I'm just very curious to hear a Lowther based
>>one as I could not succeed to acheive that for such a long time. Maybe I'll
>>hate them (I hope not!) at the end of the day but I still wish to hear at
>>least one. I hope Tom Ronan will help me in this when I'll be in Chicago at
>>mid May. I promise to write back what I think.
>
>Bart said :
>
>>If you are used to the Responses, I wouldn't hold out too much hope for a
>>Lowther full-range. Maybe as a mid-range horn augmented by a sub and
>>possibly also a super-tweeter.
>>
>
>Don't make up your mind until you hear Lowthers with the Oris front horns
>and a good subwoofer. It's a different sound than you are probably used to,
>but one I think that you will like very much. The top end lacks for
>nothing in these
>horns. Back horns are not nearly as good. You won't hate front horn Lowthers
>I can assure.
>
>Make sure Tom has the Oris horns with a good subwoofer and the phase
>extenders installed from Bert Doppenberg before you go to visit him. He's
>currently using a 46 amp (with 1.25 watts!), but the Lowthers are not hurting
>for power at all.
>
>BTW, I am also using a very simple 5842 + 46 amp on my Lowthers now.
>
>My 2 cents,
>
> - Ralph
visit my personal "NUANCE & FLUENCE" web site:
http://www.arduman.com/aa
tel: +90-216-310 44 70 (w)
fax: +90-216-343 42 01
e-mail: adnana@turk.net
=========================================================================
From: TubeGarden@aol.com
Subject: Re: [JN] 20Hz-20,000Hz, +/-3db .. but at what level?
Date: Sat, 10 Jun 2000 22:46:48 EDT
Source: Sound Digest Archive v02.n574
Greets!
Your listening room is also affected by level.
So are your ears.
It is all hopeless :)
The perfect anechoic chamber gives accurate, repeatable measurements which
are not much help in tuning your real world listening room.
I just keep tweaking everything in my listening room. I know I cannot
reproduce my fine sound in some other room. I do not care. I am retired, I do
not have to.
Audio Anarchy Lives!
I also know I could create fine sound in another room, but NOT the SAME fine
sound.
This is simple empirical experience.
It won't sell in mass quantities, Thank God.
Happy Ears!
Al B^}
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From: "Sellek, Grant (TSA)" <Grant.Sellek@transport.sa.gov.au>
Subject: [JN] 20Hz-20,000Hz, +/-3db .. but at what level?
Date: Sun, 11 Jun 2000 11:20:40 +0930
Source: Sound Digest Archive v02.n574
An interesting post off a local newsgroup. Reminds me of some
of Tom Dunker's wonderful posts a few years back on the
advantages of a highly efficient speaker. Remember them?
Grant Sellek, Adelaide, Australia
Philip Vafiadis <philipv@camtech.net.au> wrote in message
news:<15p05.13011$N4.471695@ozemail.com.au>...
> Very good observation. This is a very complicated issue...most
manufactures
> 'measure' at 1 watt...however 'measure' might be somewhat of an
> overstatement with regard to many performance claims. Some issues as
> follows: (As usual this is simplified 'plain English explanation'..those
> readers with higher level Tech knowledge should be able to fill in the
gaps)
>
> 1)
> Displacement related compression.
>
> Most woofers only move proportionately to their input signal for only a
part
> of their total travel....a typical 210mm woofer might move a total of
> +/-10mm (20mm Overall) but it's 'linear' travel may only be +/-3mm
(overall
> 6mm). As the volume level is increased a point will come when displacement
> limited compression is encountered. ie As you wind up the volume the bass
> will not increase as much as the treble in a two way system....This will
> result in a frequency vs amplitude response that stays the same up to a
> point and then changes as compression 'sets in'. The 210mm woofer in our
> DC-X moves 25mm overall and, if I remember right, 11mm linear....that's
> almost 6dB more volume potential before obvious compression sets in.
>
> 2)
> Temperature related compression.
>
> The electro-mechanical model developed around loudspeakers are not too bad
> these days...programs like LEAP and others can predict the outcomes of
these
> effects reasonably reliably (not exactly though). If you make a quick
> measurement the voice coil does not get too hot...if you run the speaker
at
> full power for 10min then repeat the test some differences will be
expected.
> Not only does voice coil resistance change when hot (and consequently
driver
> Q) but also the magnetic system may behave differently. For those who are
> not sure how much of an issue temperature is in a loudspeaker driver
should
> touch a 45W light bulb...Ouch!!! now imagine that heat going into your
> speakers for, say, half an hour....even a big lump of metal (like a
speaker
> motor) will get quite warm...and that's just with 45Watts continuously. PA
> people usually only consider 'large signal' performance and almost
disregard
> low level performance as their equipment is almost always driven VERY
hard.
>
> 3)
> Measurement inaccuracies
>
> This will come as a big surprise for many readers .... VERY few speaker
> manufactures have facilities that allow them to measure accurately. Most,
> including us, use FFT or MLS based measurement techniques as that rely on
a
> mathematical sequence of noise fed to a speaker under test that is picked
up
> by a mic and processed by a computer...these software based systems are
very
> cheap... starting at around $1,000 and going up to around $50,000. Despite
> the great 'power' available with these new tools they are also limited in
> normal labs. These tools appear attractive as it is possible to
> differentiate the direct signal from the speaker and the reflections off
the
> lab walls and floors etc....the problem is that as you start to 'gate' out
> the reflection the maths becomes less reliable at lower
frequencies.....the
> shorter the time period the less reliable the low frequency
> measurement......There is NO substitute for anechoic measurements...VAF is
> one of the few speaker companies in the world that has a wide frequency
> range anechoic chamber...ours has 1.5 metres of foam on the walls!
>
> 4)
> What distance to measure at.
>
> Most frequency response measurements are taken at around 1 Metre, while
> 'sort of' a standard distance, it is a 'stupid' distance.....almost no-one
> listens at 1 Metre. VAF measure at between 2 Metres and 3.5 Metres
depending
> on the speaker...statistically most people listen at between 2.5 M and
3.5M
> from their speakers.
>
> With regard to your question, "Is there any point in comparing freq
> responses claims between manufacturers?" A little...but not much
> point...Phase response, Stored energy (cumulative Spectral Decay), power
> response (total speaker radiation) etc should also be compared.......My
> guess is that fewer than 10% of speaker manufactures would be in a
position
> to reliably make these measurements.... most published measurements are
VERY
> flawed....When you are comparing figures find out what facilities the
> manufacturer has...don't rely on the sales 'blurb'. At VAF we go to a
> **LOT** of trouble to ensure our measurements are valid...probably why our
> speakers were chosen for the worlds largest and most sophisticated
> electro-acoustic system or why Telstra called us when they needed acoustic
> help with their new WayPhone.
>
> Best regards
> Philip Vafiadis
> VAF Research Pty Ltd
> www.vaf.com.au
>
>
>
> scott <!spam-scottf@bigpond.net.au> wrote in message
> news:3941ECEF.14FACBA3@bigpond.net.au...
> > Just reading some speakers specs and comparing manufacturers claims for
> > frequency response.
> >
> > Most of them quote figures like '30Hz to 20kHz +/- 1.5dB' or sometimes
> > the +/-3db point.
> >
> > At what output level is this measured? If it's done at very low volume
> > levels, would that make it easier to claim a very wide, flat frequency
> > response? If it's done at high volumes, what does that imply about the
> > lower volume levels?
> >
> > Is there any point in comparing freq responses claims between
> > manufacturers? Or is this a bit like power output ratings?
> >
> > Mr Vaf might be able to answer this one (not picking on their claims
> > though...)
>
>
=========================================================================
From: Thomas Dunker <dunker@invalid.ed.ntnu.no>
Subject: Re: [JN] 20Hz-20,000Hz, +/-3db .. but at what level?
Date: Mon, 12 Jun 2000 17:25:00 +0200 (CEST)
Source: Sound Digest Archive v02.n576
On Sun, 11 Jun 2000, Sellek, Grant (TSA) wrote:
> An interesting post off a local newsgroup. Reminds me of some
> of Tom Dunker's wonderful posts a few years back on the
> advantages of a highly efficient speaker. Remember them?
> Grant Sellek, Adelaide, Australia
Yeah, I remember them (...)
Anyone who can read French should obtain a copy of Jean Hiraga's
"Les Haut-Parleurs", which has a lot of hard to find information (a lot
of graphics too) on dynamic nonlinearity phenomena in speakers. A lot of
hard to find information on speakers, period. It is without a doubt the
best single publication on speakers I have come across. Unfortunately I
don't read French very well, but maybe OCR scanning and Babel Fish...?
Most of the noteworthy distortion in speakers has been well researched
and documented. Some of the distortion phenomena were anticipated before
practical loudspeakers were a fact, and many of them are still largely
ignored.
I don't really have a lot to add to the posts I wrote a couple of years
back. I already know the challenges well enough to keep me preoccupied
a few lifetimes.
I'd start with my own bottom line: Nearly all the nonlinear distortion in
electrodynamic speakers increases by proportion to the "signal", whether
input power (temperature), diaphragm/suspension excursions, modulations of
the magnetic field etc. These mechanisms cause dynamic compression, like
a thermal/mechanic dynamics compressor, and along with compression,
amplitude dependent phase and frequency response changes, interaction with
crossovers (if passive) and amplifier, and more nasty things than I can
remember off the top of my head.
Personally, I believe the "brute force" approach to be the most effective
(and least profitable), since ALL electrodynamic speakers possess the same
tendency to distort more as the signal amplitude increases. When input
power and diaphragm excursions decrease, so does the distortion. To make
up for the loss of acoustic output, it is necessary to explore efficient
speakers. It seems that a lot of people have stubled across horns and
other low-distortion high efficiency speakers merely because they happened
to like low power amps. This is fine by me, but I have focused on the
intrinsic low distortion of such speakers.
Conversely, since amp power got so cheap way back half a century ago,
nobody feels that they "need" efficient speakers anymore, wrongly
believing that the only thing about efficient speakers is the efficiency.
Efficient speakers are efficient for good reasons: Efficient motors and
efficient radiators. Less stress, period. They sound that way, too, if
properly designed.
It's been quiet from my corner for a long while. The audio hobby has been
kind of dormant lately, but I'm beginning to get the itch again...
I used to build stuff at a shop at the tech college, but now it's a bit
too far off that I can go there frequently, so part of the summer's plans
is to get a workbench here at home so I can get some tings done again,
every time I have a few odd hours to spare.
I grew so frustrated with the lack of more or less creative hobby
activities that a copule of weeks ago I went out and bought myself another
hobby. I have not played an instrument in years (trombone in the school
band AGES ago) and don't even sing in a choir anymore and I resolved that
I want to learn to play an instrument. They say it's never too late...
I've tried the trombone, recorder and guitar, but it was never that much
FUN. Then, for the past few years I've listened to a lot of Jethro Tull
and grew increasingly intrigued with the flute. I decided I wanted to buy
a flute, and so I did, a couple of weeks ago. A used Yamaha YFL-22S,
an old student model similar to the current YFL-221S. I took it home, and
the minute I got some clean tones out of it, I was hooked. Wow, what FUN
to play! So I play the flute now as often as I can, trying to reteach
myself reading notes and playing children's tunes. When I have the time
and money I will take some lessons.
What preoccupies me even more these days is my new girlfriend, who I met
on New Year's Eve. When I'm not at work, I spend a lot of my time with
her, having the greatest time. She's fun, cute, smart and lovely and kind
and the best friend I've ever had. I know I've found "the one". I mean,
this time I just *know* - and so does she.
Eventually I hope to wipe the dust off some of my unfinished projects and
probably to get started with something new.
And to whoever is going to Århus this summer, I'll be there...
Still tuned in
Tom
- ------------------------------------------------------------------------
_/\_ Thomas Dunker \ The Horn Speaker Home Page:
/ \ P.O.Box 2811 \ http://invalid.ed.ntnu.no/~dunker/horns.html
| | 7002 Trondheim \
| | NORWAY \--\ "Those with head above water
\____/ dunker@omegav.ntnu.no \ see only the tip of the iceberg"
|||| phone: (+47)73911068 \ (Gene Dalby)
- ------------------------------------------------------------------------
=========================================================================
From: "Le Cleac'h J.-M." <lecleach@cgi.ensmp.fr>
Subject: Re: [JN] 20Hz-20,000Hz, +/-3db .. but at what level?
Date: Tue, 13 Jun 2000 13:59:46 +0200
Source: Sound Digest Archive v02.n577
- ----------
> De : Thomas Dunker <dunker@invalid.ed.ntnu.no>
> A : Sellek, Grant (TSA) <Grant.Sellek@transport.sa.gov.au>
> Cc : 'Sound Practices' <sound@lists.io.com>
> Objet : Re: [JN] 20Hz-20,000Hz, +/-3db .. but at what level?
> Date : lundi 12 juin 2000 17:25
Thomas Dunker,
> and grew increasingly intrigued with the flute. I decided I wanted to buy
> a flute, and so I did, a couple of weeks ago. A used Yamaha YFL-22S,
> an old student model similar to the current YFL-221S. I took it home, and
> the minute I got some clean tones out of it, I was hooked. Wow, what FUN
> to play!
Wow!!
I never could emit a single note (pure tone or distorted) with a flute (and
have good nails, that's why for me the instrument is electric guitar)!
> What preoccupies me even more these days is my new girlfriend, who I met
> on New Year's Eve. When I'm not at work, I spend a lot of my time with
> her, having the greatest time. She's fun, cute, smart and lovely and kind
> and the best friend I've ever had. I know I've found "the one". I mean,
> this time I just *know* - and so does she.
> And to whoever is going to Århus this summer, I'll be there...
Did she will be there to? Too bad I am invited (from long time so I
couldn't say no that time) in Corsica and cannot come in Arhus...
Best regards,
Jean-Michel Le Cleac'h, Paris, France
=========================================================================
From: "Thomas Sylvester" <TRS@carlsmith.com>
Subject: Re: [JN] 20k tubes
Date: Fri, 23 Mar 2001 07:52:46 -1000
Source: Sound Digest Archive v02.n840
How about 801A/VT62?
>>> Buschmann <bmann@nexgo.de> 03/22/01 10:08PM >>>
t
may i stress your nerves again? it is still the transformer
pre - opt is 20k/600 ohm, tube is 76 as anode follower.
any other candidates? with a little more uuumphh, eventualy??
a
=========================================================================
From: Buschmann <bmann@nexgo.de>
Subject: [JN] 20k tubes
Date: Fri, 23 Mar 2001 09:08:07 +0100
Source: Sound Digest Archive v02.n840
thank you sirs,
for your answers, concerning the sound of batteries..i have
to experiment..
may i stress your nerves again? it is still the transformer
pre - opt is 20k/600 ohm, tube is 76 as anode follower.
any other candidates? with a little more uuumphh, eventualy??
and ,by the way: what to do with a pair of ev sp 8??
thanks
jörg
=========================================================================
From: Joe Roberts <jroberts@io.com>
Subject: [JN] $20/pr xfmrs SOLD OUT-tnx!
Date: Mon, 05 Jul 1999 09:51:26 +0000
Source: Sound Digest Archive v02.n194
=========================================================================
From: "Paul De Raymond Leclercq" <Pderl@btinternet.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Fri, 6 Jul 2001 10:06:34 -0700
Source: Sound Digest Archive v02.n921
Hello.
I doubt that this is a viable scheme.
First the operating points: typical bias on a 211 is about -65V; with the
845 it would be around -200 - 250V and with the 805 perhaps 0 or -10V.
This shows the different characters of these three valves. Considerable
re-design would be necessary
Wavac, I believe has made 805 amplifiers, but the the valve is designed as a
Class B/C transmitter and is intended to be driven with real power. You
would need a driver transformer
845 was designed to be an audio valve and modulator. This and its rarity
explain why it is now so costly. It has very low mu (compare mu of 3 with
the 805's 140!). Here you have traded driving with Power for driving with
Voltage.
The different characteristics of these types dictate the type of output
transformer needed. Assuming that these amplifiers are single-ended, the
primary impedance of the 211 OPT is probably about 10k. With 845 you would
probably be looking at 4 - 5k.
Finally I might add that I built a p-p amplifier using 211s. The output
transformer (I now realise) should have been 20k a-a (which would probably
make it not hi-fi). I was using 7k and got 15W for considerable expenditure
of power!. I then changed to 845s; heavily modifying the driver stage to
deliver the necessary volts at low output resistance (to drive the
capacitance of the 845). I then got 50W.
The end of this story is that I then converted to triode-strapped 813s.
These are almost as easy to drive as 211, but have anode resistance similar
to 845. A 7k (p-p) transformer suffices (with 850V on the anodes) and I
get still more power - about 60W.
I hope that some of this helps.
Best wishes
Paul Leclercq
- ----- Original Message -----
From: Snoopy <tcma@netvigator.com>
To: <sound@io.com>
Sent: Thursday, July 05, 2001 9:18 PM
Subject: [JN] 211 vs 845 vs 805
> Hi,
>
> I have the chance of buying a pair of chinese-made 211 se monoblocks.
> Each monoblock is using one 6sn7, one 6sl7 and one 211. I am wondering if
> it can be easily adapted to use 845 or 805 instead.
>
> 1. For se design, what's the difference between 211 and 845 in terms of
> sound quality, operating points and power output?
>
> 2. How about the difference between 845 and 805?
>
> 3. Is there any se or pp schematics using the 805? Is the 805
suitable
> for audio?
>
> I have a pair of G.E. 211 acquired from Edward Billeci long ago. I
know
> that vintage NOS 845 is expensive, but my friend can offer some United 805
> to me at a reasonable price. Quice interesting to know that the plate of
> 805 is at the top of the tube.
>
> Any advice/information is greatly appreciated. Thank you in advance.
>
> Best Regards,
>
> Tung-cheung MA
> HONG KONG
> 6 July 2001
>
=========================================================================
From: "Snoopy" <tcma@netvigator.com>
Subject: [JN] 211 vs 845 vs 805
Date: Fri, 6 Jul 2001 12:18:03 +0800
Source: Sound Digest Archive v02.n921
Hi,
I have the chance of buying a pair of chinese-made 211 se monoblocks.
Each monoblock is using one 6sn7, one 6sl7 and one 211. I am wondering if
it can be easily adapted to use 845 or 805 instead.
1. For se design, what's the difference between 211 and 845 in terms of
sound quality, operating points and power output?
2. How about the difference between 845 and 805?
3. Is there any se or pp schematics using the 805? Is the 805 suitable
for audio?
I have a pair of G.E. 211 acquired from Edward Billeci long ago. I know
that vintage NOS 845 is expensive, but my friend can offer some United 805
to me at a reasonable price. Quice interesting to know that the plate of
805 is at the top of the tube.
Any advice/information is greatly appreciated. Thank you in advance.
Best Regards,
Tung-cheung MA
HONG KONG
6 July 2001
=========================================================================
From: "Sellek, Grant (TSA)" <Grant.Sellek@transport.sa.gov.au>
Subject: RE: [JN] 211 vs 845 vs 805
Date: Fri, 6 Jul 2001 14:09:12 +0930
Source: Sound Digest Archive v02.n921
A 211 is much easier to drive than an 845. The 6SN7/6SL7 front
end of the 211 amps will not drive an 845. A significant
redesign of the front end is recommended: at the minimum you
*might* get away with adding a step-up IT to drive an 845, but
this could not be determined without some familiarity with the
211 amp's topology and operating points.
Recommendation: 211 amps can be very beautiful -- better to
try to optimise the amp as a 211 amp.
Grant
Grant Sellek, Adelaide, Australia
- -----Original Message-----
From: Snoopy [mailto:tcma@netvigator.com]
Sent: Friday, 6 July 2001 1:48 PM
To: sound@io.com
Subject: [JN] 211 vs 845 vs 805
Hi,
I have the chance of buying a pair of chinese-made 211 se monoblocks.
Each monoblock is using one 6sn7, one 6sl7 and one 211. I am wondering if
it can be easily adapted to use 845 or 805 instead.
1. For se design, what's the difference between 211 and 845 in terms of
sound quality, operating points and power output?
2. How about the difference between 845 and 805?
3. Is there any se or pp schematics using the 805? Is the 805 suitable
for audio?
I have a pair of G.E. 211 acquired from Edward Billeci long ago. I know
that vintage NOS 845 is expensive, but my friend can offer some United 805
to me at a reasonable price. Quice interesting to know that the plate of
805 is at the top of the tube.
Any advice/information is greatly appreciated. Thank you in advance.
Best Regards,
Tung-cheung MA
HONG KONG
6 July 2001
=========================================================================
From: Grover Gardner <groverg@postoffice.att.net>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Fri, 06 Jul 2001 17:04:00 -0400
Source: Sound Digest Archive v02.n921
Paul De Raymond Leclercq wrote:
>
> Hello.
>
> I doubt that this is a viable scheme.
>
> First the operating points: typical bias on a 211 is about -65V; with the
> 845 it would be around -200 - 250V and with the 805 perhaps 0 or -10V.
>
> This shows the different characters of these three valves. Considerable
> re-design would be necessary
Yes, the tubes are very different in terms of bias voltage and drive
requirements, but the 845 only needs -150 volts bias in Class A at
1200VDC. Still that's a hefty difference.
The 845 also has a mu of 8, I believe.
Sonically, I've played with all these tubes a bit, the 845 most of all.
I like its deep, weighty sound and warmth. The 211 is cooler and
sweeter but a bit veiled for my tastes. Nonetheless there have been a
lot fine, musical amps built with this tube. You can also drive the 211
into A2, which you cannot do with the 845, so the 211 can approach good
power levels with the right circuit.
The 805 wants positive grid bias and so is difficult to master. The
sound is *quite* different from either of the other two. Taught, clean,
analytical, but also musical. In the right hands I suspect it can sing
mightily, combining the qualities of the 845 and the 211. In the wrong
hands (like mine) you can quickly get into trouble with grid-current
issues, distortion, etc. :-) Not for beginners!
For Class A at about 1200VDC, the same output tranny should work for
either the 211 or 845, 10K being the standard in most designs.
The 813 in triode is very interesting, as Paul points out. It combines
the deep sound of the 845 with a lighter, faster approach and is easier
to drive. They are readily available, going especially cheaply at
hamfests and on eBay. I've dropped it into a number of my SE 845
circuits, lowering (or is it raising?) the bias voltage to accomodate
it. It works quite well. There is an issue of a slightly peaky, edgy
sound to the highs that I've never quite gotten past, sort of what you'd
expect from a triode-wired pentode, if you know what I mean. I haven't
spent sufficient time playing with it to see if I can get rid of it.
Other than that it's a lot of fun to play with. You could probably drop
it into a 211 circuit with appropriate bias adjustment and get a taste
of the warmer, 845-like sound.
- --
Grover Gardner
groverg@postoffice.att.net
Visit my web site at http://home.att.net/~groverg/homepage.htm
=========================================================================
From: Richard C Nevill <rnevill@is.dal.ca>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Fri, 6 Jul 2001 23:25:02 -0300 (ADT)
Source: Sound Digest Archive v02.n921
Okay,
Being new to this tube stuff I have a pair of RCA 811A's ( Jeremy E.
didn't you want them?), a single GE DR-811 and a couple of 866's, one
globe and the other coke bottle.
So besides the big B+'s these need are they any good as audio tubes?
Seeing in the subject 800 series tubes I thought I would ask. I believe I
read somewhere that during Desert Storm the SS radios the US was using had
problems with the sand and they dug out all their old tube stuff that used
811's. After that no problems
Well, cheers gang
Richard Nevill
=========================================================================
From: "Paul De Raymond Leclercq" <Pderl@btinternet.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Fri, 6 Jul 2001 23:36:59 -0700
Source: Sound Digest Archive v02.n921
Hello.
> but the 845 only needs -150 volts bias in Class A at
> 1200VDC. Still that's a hefty difference.
I have just had a look at the data for 845. At 1.2kV and -150V, the valve
would be passing about 135mA, i.e. 162W - more than double its 75W Pa limit.
At 1.2kV you would need bias of about -180V to run 63mA which would give you
75W Pa.
>
> The 845 also has a mu of 8, I believe.
I was wrong too! It is 5.3
> There is an issue of a slightly peaky, edgy sound to the highs that I've
never quite gotten past, sort of what you'd expect from a triode-wired
pentode, if you know what I mean. > --
This is very interesting; when I changed from 845s to 813s (at 980V) the
first thing I noticed was increased delicacy in the treble; it goes to show
that one man's peakiness is another's music!
Regards to all
Paul
=========================================================================
From: "Paul De Raymond Leclercq" <Pderl@btinternet.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Sat, 7 Jul 2001 09:18:18 -0700
Source: Sound Digest Archive v02.n921
Hello.
866 is a mercury vapour rectifier; this one can give you about 5kV at a
quarter of an amp!
811 has its fans - there is a version manufactured by Svetlana. I believe
that this type is used in what is known as "Class A2", where some grid
current is drawn and a driver transformer is required..
From my point of view the rarity of true audio types is frustrating; many of
the rf types are very attractive. As an example I have some 826s; these
look superb lit up but judging by what my valve tester tells me, they are
strictly class C. Grrrrrr!
Best wishes
Paul
- ----- Original Message -----
From: Richard C Nevill <rnevill@is.dal.ca>
To: Grover Gardner <groverg@postoffice.att.net>
Cc: <sound@io.com>
Sent: Friday, July 06, 2001 7:25 PM
Subject: Re: [JN] 211 vs 845 vs 805
>
> Okay,
>
> Being new to this tube stuff I have a pair of RCA 811A's ( Jeremy E.
> didn't you want them?), a single GE DR-811 and a couple of 866's, one
> globe and the other coke bottle.
>
> So besides the big B+'s these need are they any good as audio tubes?
> Seeing in the subject 800 series tubes I thought I would ask. I believe I
> read somewhere that during Desert Storm the SS radios the US was using had
> problems with the sand and they dug out all their old tube stuff that used
> 811's. After that no problems
>
> Well, cheers gang
>
> Richard Nevill
>
>
>
>
>
=========================================================================
From: Grover Gardner <groverg@postoffice.att.net>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Sat, 07 Jul 2001 21:36:56 -0400
Source: Sound Digest Archive v02.n921
Paul De Raymond Leclercq wrote:
>
> Hello.
> > but the 845 only needs -150 volts bias in Class A at
> > 1200VDC. Still that's a hefty difference.
>
> I have just had a look at the data for 845. At 1.2kV and -150V, the valve
> would be passing about 135mA, i.e. 162W - more than double its 75W Pa limit.
> At 1.2kV you would need bias of about -180V to run 63mA which would give you
> 75W Pa.
Well, at 950VDC Class A I've never had to bias them at more than -120
for 80mA. That's the Chinese version, anyway. But AB PP would be
another matter...
> >
> > The 845 also has a mu of 8, I believe.
>
> I was wrong too! It is 5.3
>
> > There is an issue of a slightly peaky, edgy sound to the highs that I've
> never quite gotten past, sort of what you'd expect from a triode-wired
> pentode, if you know what I mean. > --
>
> This is very interesting; when I changed from 845s to 813s (at 980V) the
> first thing I noticed was increased delicacy in the treble; it goes to show
> that one man's peakiness is another's music!
Yes, but we're talking PP versus SE here, no? I suspect there are some
characteristics that appear in SE that are cancelled or ameliorated in
PP. I'm not the only one who has noticed this--Roscoe Primrose also
noticed the same thing. However, I think that a little work with the
tube in SE could perhaps solve the problem. It's still worth pursuing
for the advantages it offers.
- --
Grover Gardner
groverg@postoffice.att.net
Visit my web site at http://home.att.net/~groverg/homepage.htm
=========================================================================
From: j45yip@netscape.net (Johari Yip)
Subject: Re: [JN] 211 vs 845 vs 805
Date: Sun, 08 Jul 2001 00:49:31 -0400
Source: Sound Digest Archive v02.n921
"Paul De Raymond Leclercq" <Pderl@btinternet.com> wrote:
>
> From my point of view the rarity of true audio types is frustrating; many of
> the rf types are very attractive. As an example I have some 826s; these
> look superb lit up but judging by what my valve tester tells me, they are
> strictly class C. Grrrrrr!
>
> Best wishes
>
> Paul
Hi Paul,
At the moment, I'm working on a circuit that appeared in Shishido's transmitter tube book using the
826. The circuit uses a NC10 i/t to drive the 826 into classA2. The driver tube is the 6em7 used in
the standard configuration with about 30ma running thru the second ttiode half. I can't get my hands
on the NC10 and thought of using the EP 1:1 i/t instead...anybody has idea if this will work in pla
ce of the NC10?
Yes, the 826 do light up beautifully...8^)
- --
Johari Yip
===================
j45yip@netscape.net
===================
__________________________________________________________________
Get your own FREE, personal Netscape Webmail account today at http://webmail.netscape.com/
=========================================================================
From: "Paul De Raymond Leclercq" <Pderl@btinternet.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Sun, 8 Jul 2001 11:29:11 -0700
Source: Sound Digest Archive v02.n921
Hello Grover, everybody.
> Well, at 950VDC Class A I've never had to bias them at more than -120
> for 80mA. That's the Chinese version, anyway. But AB PP would be
> another matter...
Yes, I ran mine in push-pull (they were the Chinese ones too) but Class A.
This was about three years ago and my memory is a bit hazy. Va was 980V and
bias about -150 which suggest that I was running 60mA per valve.
>
> > Yes, but we're talking PP versus SE here, no? I suspect there are some
> characteristics that appear in SE that are cancelled or ameliorated in
> PP. I'm not the only one who has noticed this--Roscoe Primrose also
> noticed the same thing. However, I think that a little work with the
> tube in SE could perhaps solve the problem. It's still worth pursuing
> for the advantages it offers.
Yes, the amplifier is now entirely differential and driven by balanced line
from yet more differentials in the line stage (got to find a way to use up
some of the valves that are enguilfing my little flat!).. Obviously
perfromance and sound will be very different; the books say that even-order
harmoniscs will be cancelled and odd-orders doubled.
Regards
PAul
=========================================================================
From: "Paul De Raymond Leclercq" <Pderl@btinternet.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Sun, 8 Jul 2001 11:34:12 -0700
Source: Sound Digest Archive v02.n921
Johari,
thanks for that; I shall be interested to hear of your progress. I am
afraid that I have no knowledge of interstage transformers, so I cannot
help.
Regards
Paul
- ----- Original Message -----
From: Johari Yip <j45yip@netscape.net>
To: <pderl@btinternet.com>
Cc: <sound@io.com>
Sent: Saturday, July 07, 2001 9:49 PM
Subject: Re: [JN] 211 vs 845 vs 805
"Paul De Raymond Leclercq" <Pderl@btinternet.com> wrote:
>
> From my point of view the rarity of true audio types is frustrating; many
of
> the rf types are very attractive. As an example I have some 826s; these
> look superb lit up but judging by what my valve tester tells me, they are
> strictly class C. Grrrrrr!
>
> Best wishes
>
> Paul
Hi Paul,
At the moment, I'm working on a circuit that appeared in Shishido's
transmitter tube book using the 826. The circuit uses a NC10 i/t to drive
the 826 into classA2. The driver tube is the 6em7 used in the standard
configuration with about 30ma running thru the second ttiode half. I can't
get my hands on the NC10 and thought of using the EP 1:1 i/t
instead...anybody has idea if this will work in place of the NC10?
Yes, the 826 do light up beautifully...8^)
- --
Johari Yip
===================
j45yip@netscape.net
===================
__________________________________________________________________
Get your own FREE, personal Netscape Webmail account today at
http://webmail.netscape.com/
=========================================================================
From: TubeGarden@aol.com
Subject: [JN] 211 vs 845 vs 805
Date: Sun, 8 Jul 2001 09:06:37 EDT
Source: Sound Digest Archive v02.n922
- --part1_e8.173a91e3.2879b4dd_boundary
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
In a message dated 7/8/01 3:33:31 AM US Mountain Standard Time,
Pderl@btinternet.com writes:
> Yes, the amplifier is now entirely differential and driven by balanced line
> from yet more differentials in the line stage (got to find a way to use up
> some of the valves that are enguilfing my little flat!).. Obviously
> perfromance and sound will be very different; the books say that even-order
> harmoniscs will be cancelled and odd-orders doubled.
>
Greets!
Using TubeCAD for SE, I find operating points which have very low distortion.
subtext: vary network id=localcdrm active
Sorry, my brain just slipped a couple decades, where was...
oh, yes, while these 'low points" are not wide band, I am working under the
illusion that idle clarity, clarity at idle, supports low level detail :)
Someday I will hook up my 334A and measure,,,
The fake law pots are terrific, NTE formed carbon linear 2W 25K $6.95 :)
Happy Ears!
Al B^}
- --part1_e8.173a91e3.2879b4dd_boundary
Content-Type: text/html; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
<HTML><FONT FACE=arial,helvetica><BODY BGCOLOR="#ffffff"><FONT SIZE=2>In a message dated 7/8/01 3:3
3:31 AM US Mountain Standard Time,
<BR>Pderl@btinternet.com writes:
<BR>
<BR>
<BR><BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px
; PADDING-LEFT: 5px">Yes, the amplifier is now entirely differential and driven by balanced li
ne
<BR>from yet more differentials in the line stage (got to find a way to use up
<BR>some of the valves that are enguilfing my little flat!).. Obviously
<BR>perfromance and sound will be very different; the books say that even-order
<BR>harmoniscs will be cancelled and odd-orders doubled.
<BR></BLOCKQUOTE></FONT><FONT COLOR="#000000" SIZE=3 FAMILY="SANSSERIF" FACE="Arial" LANG="0">
<BR>
<BR>Greets!
<BR>
<BR>Using TubeCAD for SE, I find operating points which have very low distortion.
<BR>
<BR>subtext: vary network id=localcdrm active
<BR>
<BR>Sorry, my brain just slipped a couple decades, where was...
<BR>
<BR>oh, yes, while these 'low points" are not wide band, I am working under the
<BR>illusion that idle clarity, clarity at idle, supports low level detail :)
<BR>
<BR>Someday I will hook up my 334A and measure,,,
<BR>
<BR>The fake law pots are terrific, NTE formed carbon linear 2W 25K $6.95 :)
<BR>
<BR>Happy Ears!
<BR>Al B^}
<BR>
<BR></FONT></HTML>
- --part1_e8.173a91e3.2879b4dd_boundary--
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] 211 vs 845 vs 805
Date: Mon, 09 Jul 2001 10:49:53 -0400
Source: Sound Digest Archive v02.n922
i have had suprisingly very good results with SV572-160
(very similar to RCA 811A characteristics) in class A2.
running at only 500V or so.
bias between +18 to +30V.
http://www.geocities.com/bobdanielak/sesv572-160.gif
this version uses cathode drive (grounded grid) in the output stage
(which is neat when you use IT drive, because you can cancel DC flux
if you play your cards right).
but it sounds just as good with plain old grid drive.
steve bench also published some great work on A2 amps in general,
but specifically used the sv572-160, too.
the 811A ought to drop right in to that amp, as well.
plate caps are cool!
bob.d.
> ----------
> From: Richard C Nevill[SMTP:rnevill@is.dal.ca]
> Sent: Friday, July 06, 2001 10:25 PM
> To: Grover Gardner
> Cc: sound@io.com
> Subject: Re: [JN] 211 vs 845 vs 805
>
>
> Okay,
>
> Being new to this tube stuff I have a pair of RCA 811A's ( Jeremy E.
> didn't you want them?), a single GE DR-811 and a couple of 866's, one
> globe and the other coke bottle.
>
> So besides the big B+'s these need are they any good as audio tubes?
> Seeing in the subject 800 series tubes I thought I would ask. I believe I
> read somewhere that during Desert Storm the SS radios the US was using had
> problems with the sand and they dug out all their old tube stuff that used
> 811's. After that no problems
>
> Well, cheers gang
>
> Richard Nevill
>
>
>
>
>
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] 211 vs 845 vs 805
Date: Mon, 09 Jul 2001 11:09:08 -0400
Source: Sound Digest Archive v02.n922
class A2 is not as bad as you might think.
if you have a decent driver, it can sound very good.
steve bench has done a lot of detailed study on A2 operation:
http://members.aol.com/sbench/a2part1.html
and he comes up with a driver that doesn't resort to transformers.
i've tried both ways, and have been lucky to have a few 10:1
step-down transformers that do the trick.
i've also experimented with the 826 (thanks to gary kaufman).
this was in a circuit very similar to my SE 833 amp:
http://www.geocities.com/bobdanielak/se833nynoise.gif
the filament voltage for the 826 is 7.5V, but i was able to
run the 826 from 6.3VCT.
i used anywhere between +10 and +25V of positive bias, with a B+
supply of 500 to 660V.
within their power limits, all of these medium mu (30 to 35)
transmitting tubes all performed well.
they seem to share a similar sonic signature, too.
so the final choice can be left to visual appeal.
the 826 is cute, the 812 looks like an 807 or 811A,
the eimac 250-th is really cool, too.
the 833, though, is the most radical of the lot...
there are plenty more to choose from.
have a blast...
> Hello.
>
> 866 is a mercury vapour rectifier; this one can give you about 5kV at a
> quarter of an amp!
>
> 811 has its fans - there is a version manufactured by Svetlana. I
> believe
> that this type is used in what is known as "Class A2", where some grid
> current is drawn and a driver transformer is required..
>
> From my point of view the rarity of true audio types is frustrating; many
> of
> the rf types are very attractive. As an example I have some 826s; these
> look superb lit up but judging by what my valve tester tells me, they are
> strictly class C. Grrrrrr!
>
> Best wishes
>
> Paul
> ----- Original Message -----
> From: Richard C Nevill <rnevill@is.dal.ca>
> To: Grover Gardner <groverg@postoffice.att.net>
> Cc: <sound@io.com>
> Sent: Friday, July 06, 2001 7:25 PM
> Subject: Re: [JN] 211 vs 845 vs 805
>
>
> >
> > Okay,
> >
> > Being new to this tube stuff I have a pair of RCA 811A's ( Jeremy E.
> > didn't you want them?), a single GE DR-811 and a couple of 866's, one
> > globe and the other coke bottle.
> >
> > So besides the big B+'s these need are they any good as audio tubes?
> > Seeing in the subject 800 series tubes I thought I would ask. I believe
> I
> > read somewhere that during Desert Storm the SS radios the US was using
> had
> > problems with the sand and they dug out all their old tube stuff that
> used
> > 811's. After that no problems
> >
> > Well, cheers gang
> >
> > Richard Nevill
> >
> >
> >
> >
> >
>
=========================================================================
From: "Dave Slagle" <dslagle@earthlink.net>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Mon, 09 Jul 2001 15:02:03 -0400
Source: Sound Digest Archive v02.n922
> At the moment, I'm working on a circuit that appeared in Shishido's
> transmitter tube book using the 826. The circuit uses a NC10 i/t to drive
> the 826 into classA2. The driver tube is the 6em7 used in the standard
> configuration with about 30ma running thru the second ttiode half. I can't
> get my hands on the NC10 and thought of using the EP 1:1 i/t
> instead...anybody has idea if this will work in place of the NC10?
> Yes, the 826 do light up beautifully...8^)
i think the NC-10 is one of the units designed for IIT (inverted interstage
transformer) usage, so the EP will not replace it. it will work though if
you bias the 826 negatively... the ep trannie is bifilar and you cannot
reverse polarity of the secondary for iit usage.
dave
=========================================================================
From: "Snoopy" <tcma@netvigator.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 00:32:47 +0800
Source: Sound Digest Archive v02.n922
Dear all,
Thanks all for the advice. I will stick to the 211 for the time being,
and tweak it to suit my taste.
Best Regards,
Tung-cheung MA
HONG KONG
- ----- Original Message -----
From: "Snoopy" <tcma@netvigator.com>
To: <sound@io.com>
Sent: Friday, July 06, 2001 12:18 PM
Subject: [JN] 211 vs 845 vs 805
> Hi,
>
> I have the chance of buying a pair of chinese-made 211 se monoblocks.
> Each monoblock is using one 6sn7, one 6sl7 and one 211. I am wondering if
> it can be easily adapted to use 845 or 805 instead.
>
> 1. For se design, what's the difference between 211 and 845 in terms of
> sound quality, operating points and power output?
>
> 2. How about the difference between 845 and 805?
>
> 3. Is there any se or pp schematics using the 805? Is the 805
suitable
> for audio?
>
> I have a pair of G.E. 211 acquired from Edward Billeci long ago. I
know
> that vintage NOS 845 is expensive, but my friend can offer some United 805
> to me at a reasonable price. Quice interesting to know that the plate of
> 805 is at the top of the tube.
>
> Any advice/information is greatly appreciated. Thank you in advance.
>
> Best Regards,
>
> Tung-cheung MA
> HONG KONG
> 6 July 2001
>
=========================================================================
From: SBench@aol.com
Subject: Re: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 00:49:39 EDT
Source: Sound Digest Archive v02.n922
In a message dated 01-07-09 11:14:26 EDT, robert.m.danielak@lmco.com writes:
> class A2 is not as bad as you might think.
> if you have a decent driver, it can sound very good.
>
> steve bench has done a lot of detailed study on A2 operation:
>
> http://members.aol.com/sbench/a2part1.html
>
> and he comes up with a driver that doesn't resort to transformers.
>
> i've tried both ways, and have been lucky to have a few 10:1
> step-down transformers that do the trick.
>
> i've also experimented with the 826 (thanks to gary kaufman).
>
> this was in a circuit very similar to my SE 833 amp:
>
> http://www.geocities.com/bobdanielak/se833nynoise.gif
>
> the filament voltage for the 826 is 7.5V, but i was able to
> run the 826 from 6.3VCT.
>
> i used anywhere between +10 and +25V of positive bias, with a B+
> supply of 500 to 660V.
>
> within their power limits, all of these medium mu (30 to 35)
> transmitting tubes all performed well.
>
> they seem to share a similar sonic signature, too.
>
> so the final choice can be left to visual appeal.
>
Hi Bob and all,
Agree 100%. A2 with a good driver sounds N I C E. ALL of the
folks at the couple of auditions I had at work preferred the 841
to the 572-160. (driver etc was the same as noted on my web pages
on A2.). The key feature enabling the good sound was the direct
coupling. Tried cap coupling to the grid of the driver (exactly the
same quiescent point, and the driver not drawing grid current) but the
sound was VASTLY inferior.
Be prepared to hunt for (and find) several "sweet spots" in the biasing
voltage.
One big difference between the 841 and 572-160 is the microphonics.
Tap on the 572-160 and you can hear it (which is probably why it didn't
sound quite as good - acoustic feedback - not enough for oscillation but...).
Tap on the 841 and nothing. 841 was dead silent: no hiss, no hum,
no microphonics from the input 8532s, the driver 6n30pi or the 841s.
Excellent imaging, quick, accurate. Did have to change the VR tubes a few
times to get a good set of quiet ones, but once burnt in, no further issues.
Was gonna try putting in a set of 809s, but didn't have a ready set so never
got around to it, particularly since the 841s sound so dern good.
By the way, 811s or 811As drop into the circuit just fine as Bob noted.
Didn't do exhaustive tests with them, though. In hindsight, that might
not be a bad idea, as soon as I get some extra time.
Looking at the 826 specs, I'd believe that ought to work well too. Bob,
did you happen to try to see if that really nice feature (center tapped
filament) was able to buy anything? I'd expect to be able to pick up just
an extra smidgen (precise technical term) of clarity when run "parallel".
Haven't tried Bob's transformer coupling, but I'd believe that to be
an excellent choice too. The high gain of the 572-160 would also
slightly relax the drive issues in that mode.
Please note that there's a subtle but very important distinction in the
kind of A2 being discussed in this thread. The IDLE voltage and most
of the operating range is in positive grid region. This is distinctly
different than what you're probably going to see with a 211, where the
IDLE is near zero or into negative grid region.
Best Regards,
Steve
=========================================================================
From: j45yip@netscape.net (Johari Yip)
Subject: Re: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 01:30:28 -0400
Source: Sound Digest Archive v02.n922
SBench@aol.com wrote:
>
> Looking at the 826 specs, I'd believe that ought to work well too. Bob,
> did you happen to try to see if that really nice feature (center tapped
> filament) was able to buy anything? I'd expect to be able to pick up just
> an extra smidgen (precise technical term) of clarity when run "parallel".
>
Hi Steve,
Thoroughly enjoyed your article on the introduction of A2 amplifier. What a good operating point for
the 826 in classA2 then? I know most of the time, you need to 'dial-in' the sound, so to speak. Shi
shido operates the 826 at vp of 290v, +45v at the grid, i think and pri. imp. of the optx at 1k25 oh
ms. i think the 826 is drawing close to 140ma, if i'm not wrong.
- --
Johari Yip
===================
j45yip@netscape.net
===================
__________________________________________________________________
Get your own FREE, personal Netscape Webmail account today at http://webmail.netscape.com/
=========================================================================
From: pderl@btinternet.com
Subject: Re: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 12:32:59 00100
Source: Sound Digest Archive v02.n922
Hello,
I have a few 826s; are there any data for operation in
push-pull?
Obviously, conventional operation is out because of the
high anode resistance.
Perhaps operation with positive grids is an option?
Rgeards
Paul Leclercq
>In a message dated 01-07-09 11:14:26 EDT,
robert.m.danielak@lmco.com writes:
>
>> class A2 is not as bad as you might think.
>> if you have a decent driver, it can sound very good.
>>
>> steve bench has done a lot of detailed study on A2
operation:
>>
>> http://members.aol.com/sbench/a2part1.html
>>
>> and he comes up with a driver that doesn't resort
to transformers.
>>
>> i've tried both ways, and have been lucky to have a
few 10:1
>> step-down transformers that do the trick.
>>
>> i've also experimented with the 826 (thanks to
gary kaufman).
>>
>> this was in a circuit very similar to my SE 833 amp:
>>
>>
http://www.geocities.com/bobdanielak/se833nynoise.gif
>>
>> the filament voltage for the 826 is 7.5V, but i was
able to
>> run the 826 from 6.3VCT.
>>
>> i used anywhere between +10 and +25V of positive
bias, with a B+
>> supply of 500 to 660V.
>>
>> within their power limits, all of these medium mu
(30 to 35)
>> transmitting tubes all performed well.
>>
>> they seem to share a similar sonic signature, too.
>>
>> so the final choice can be left to visual appeal.
>>
>
>Hi Bob and all,
>Agree 100%. A2 with a good driver sounds N I C E. ALL
of the
>folks at the couple of auditions I had at work preferred
the 841
>to the 572-160. (driver etc was the same as noted on
my web pages
>on A2.). The key feature enabling the good sound was
the direct
>coupling. Tried cap coupling to the grid of the driver
(exactly the
>same quiescent point, and the driver not drawing grid
current) but the
>sound was VASTLY inferior.
>
>Be prepared to hunt for (and find) several "sweet
spots" in the biasing
>voltage.
>
>One big difference between the 841 and 572-160 is
the microphonics.
>Tap on the 572-160 and you can hear it (which is
probably why it didn't
>sound quite as good - acoustic feedback - not enough
for oscillation but...).
>Tap on the 841 and nothing. 841 was dead
silent: no hiss, no hum,
>no microphonics from the input 8532s, the driver
6n30pi or the 841s.
>Excellent imaging, quick, accurate. Did have to
change the VR tubes a few
>times to get a good set of quiet ones, but once burnt
in, no further issues.
>
>Was gonna try putting in a set of 809s, but didn't have
a ready set so never
>got around to it, particularly since the 841s sound so
dern good.
>
>By the way, 811s or 811As drop into the circuit just fine
as Bob noted.
>Didn't do exhaustive tests with them, though. In
hindsight, that might
>not be a bad idea, as soon as I get some extra time.
>
>Looking at the 826 specs, I'd believe that ought to
work well too. Bob,
>did you happen to try to see if that really nice feature
(center tapped
>filament) was able to buy anything? I'd expect to be
able to pick up just
>an extra smidgen (precise technical term) of clarity
when run "parallel".
>
>Haven't tried Bob's transformer coupling, but I'd
believe that to be
>an excellent choice too. The high gain of the 572-160
would also
>slightly relax the drive issues in that mode.
>
>Please note that there's a subtle but very important
distinction in the
>kind of A2 being discussed in this thread. The IDLE
voltage and most
>of the operating range is in positive grid region. This is
distinctly
>different than what you're probably going to see with a
211, where the
>IDLE is near zero or into negative grid region.
>
>Best Regards,
>Steve
>
=========================================================================
From: Roscoe Primrose <roscoe@aiko.com>
Subject: Re: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 00:10:40 -0400
Source: Sound Digest Archive v02.n923
SBench@aol.com wrote:
>> and all other things equal, i have prefered metal plate tubes over
>>
> graphite,
>
>> for some reason.
>>
>
> with one exception ---> 813
In my amp, a low-voltage triode wired 813, the metal plate fared better
every time. Only one data point though...
Peace
- --
Roscoe Primrose
- -- mailto:roscoe@aiko.com -- http://www.aiko.com/roscoe --
"Once in a while you get shown the light
In the strangest of places if you look at it right." Robert Hunter
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 19:24:00 -0400
Source: Sound Digest Archive v02.n923
> >
>
> Hi Bob and all,
> Agree 100%. A2 with a good driver sounds N I C E. ALL of the
> folks at the couple of auditions I had at work preferred the 841
> to the 572-160. (driver etc was the same as noted on my web pages
> on A2.).
>
in retrospect, i see quite a few differences between these two tubes.
correct me if i am wrong, but i thought the 841 is more of a medium mu
animal (between 30 and 40).
in this case it falls in line with 826, 812, 250-th, and many others.
the sv-572 has a mu of around 160, like 811A, 572B, 808 (i think).
the sv572-160 also has graphite plate (like 572b).
and all other things equal, i have prefered metal plate tubes over graphite,
for some reason.
i have not retrofit 811A into my 572-160 amp, but i'd bet it would sound
better.
the 572-160 amp is not too hard to take, though.
in fact, it's very nice.
> The key feature enabling the good sound was the direct
> coupling. Tried cap coupling to the grid of the driver (exactly the
> same quiescent point, and the driver not drawing grid current) but the
> sound was VASTLY inferior.
>
not suprised.
there's something fundamentally wrong with cap coupling to a A2 grid.
the changing impedance causes rectification effects whereby the signal
amplitude dynamically adjusts the instantaneous bias.
that's got to screw with the sound, right?
however, i have heard a cap coupled design (essentially a copy
of eric barbour's 1st sv811-10 amp with 6sn7 driver)
that was not half bad.
for a time i pondered whether this effect could have some
GOOD effects.
> Be prepared to hunt for (and find) several "sweet spots" in the biasing
> voltage.
>
>
this is definitely some new ground to cover:
completely ignored properties of filamentary triodes, brought to light,
maybe...
i certainly noted that in my 572-160 amp, there was a definite sweet spot
when adjusting from zero bias up toward +25V.
what was intriguing was that it occurred much earlier than i would have
thought.
in other words, at zero volts, there was practically no bias, the tube was
essentially cut-off for a big part of the audio modulation.
5V barely gave me 10 or 20mA of headroom, but the amp played loudly
with good sound.
for best linearity, my calculations said i needed about 25 to 30V,
but the sound seemed to "bloom" at 19V.
steve clued me in that these sweet spots may tend to repeat.
so i revisited this experiment.
above 5V we at least had listenable music, but the 1st bloom
seemed to cut in at 16V or so, then again at 19V, then again at 22 or 23,
and maybe again before 30V.
the definite sweet spot of them all was eithe the 19V or 23V one
(don't recall) and nothing like the predicted 28V (or whatever it was).
this apparently had nothing to do with bias headroom, linearity of operating
point, etc. this was something else...
i believe steve says it has more to do with the structure of the filament,
itself.
brilliant stuff...
> One big difference between the 841 and 572-160 is the microphonics.
> Tap on the 572-160 and you can hear it (which is probably why it didn't
> sound quite as good - acoustic feedback - not enough for oscillation
> but...).
> Tap on the 841 and nothing. 841 was dead silent: no hiss, no hum,
> no microphonics from the input 8532s, the driver 6n30pi or the 841s.
>
this is very interesting.
i recently moved my sv572-160 amp to the "audition shelf"
which sits between my speakers.
and for some reason, it did not sound as good as i had recalled.
(it has beed a few weeks since i last heard it...)
i do get some vibration in to this shelf.
maybe i need to damp it out....
> Excellent imaging, quick, accurate. Did have to change the VR tubes a few
> times to get a good set of quiet ones, but once burnt in, no further
> issues.
>
> Was gonna try putting in a set of 809s, but didn't have a ready set so
> never
> got around to it, particularly since the 841s sound so dern good.
>
> By the way, 811s or 811As drop into the circuit just fine as Bob noted.
> Didn't do exhaustive tests with them, though. In hindsight, that might
> not be a bad idea, as soon as I get some extra time.
>
i think just about any transmitting triode will drop in.
just adjust the bias (by ear!!!).
as noted above, the 811A has very high mu, so the gain may be
excessive for some tastes.
however, i switched to cathode drive and the sensitivity
drops significantly. in my case, i think it's just right...
another issue with these different tube types:
the plate resistance of the 811A/ sv572-160 is pretty high.
like 5 to 10K, compared to <5K for 801, 841, 572-30, 812, etc.
however, on just about all of these tubes, a 10k load seems to
work just fine.
i don't seem to have a problem with a damping factor around 1...
> Looking at the 826 specs, I'd believe that ought to work well too. Bob,
> did you happen to try to see if that really nice feature (center tapped
> filament) was able to buy anything?
>
no, i haven't.
but this should be easy enough to try.
i have a few small power supplies that wouldn't give me 7.5V
at the required current, but should do 3.75V...
thanks for the tip...
> I'd expect to be able to pick up just
> an extra smidgen (precise technical term) of clarity when run "parallel".
>
have to think about why this would be, but i don't doubt you...
> Haven't tried Bob's transformer coupling, but I'd believe that to be
> an excellent choice too. The high gain of the 572-160 would also
> slightly relax the drive issues in that mode.
>
yeah. even with a 10:1 step-down, it's no problem... ;)
> Please note that there's a subtle but very important distinction in the
> kind of A2 being discussed in this thread. The IDLE voltage and most
> of the operating range is in positive grid region. This is distinctly
> different than what you're probably going to see with a 211, where the
> IDLE is near zero or into negative grid region.
>
i agree. but i may have some conflicting observations...
there is fundamentally something different between an amp with
significant positive bias and a zero-bias amp.
if you use enough positive bias, you might only rarely drive the grid
below zero (into A1). for the most-part you stay in one quadrant.
in zero bias, you (attempt to) span equally into positive and negative
grid swings. you draw grid current only for about 1/2 the cycle.
the former seems intuitively better, once you've designed the driver to go
into grid current, you may as well stay there.
i've experimented with a direct coupled design that used the grid
as a load (no additional load resistor, the grid current was the load). this
seemed to be quite do-able, if i had the right
driver tube for the job (which i didn't).
a choke in parallel (essentially a choke load, that didn't take
all of the driver dc current) seemed to make it better, though.
HOWEVER, as i have found with my 833 amp, zero bias can work
and sound just as good as "deep A2" if the driver is stupid-low
in impedance (like 10 - 20 ohm).
maybe it's not the same, but increasing bias to +5, +10, +15V
did not seem to make as much difference as i would have expected.
so i am still puzzled, and intrigued.
there is still a lot of work to be done in A2.
i got laughed at 6 years ago when i started playing with a class A2 211
design.
and i've done a lot of A2 amps using sv811-10, sv-572-10/30
812, etc over the years.
but it wasn't til a few months ago that i found something
that i am SURE sounds world-class.
and the shared experiences of my esteemed collegues only helps to encourage
me and excite me.
thanks to steve, in particular, for spending the time to document your
results.
i hope more of you will pick up on this.
it is a relatively easy way to put garden-variety transmitting tubes to good
use.
and they look cool too!
gotta run,
bob.d.
=========================================================================
From: SBench@aol.com
Subject: Re: [JN] 211 vs 845 vs 805
Date: Tue, 10 Jul 2001 23:33:04 EDT
Source: Sound Digest Archive v02.n923
Hi Bob and all,
In a message dated 01-07-10 19:25:21 EDT, robert.m.danielak@lmco.com writes:
> correct me if i am wrong, but i thought the 841 is more of a medium mu
> animal (between 30 and 40).
>
> in this case it falls in line with 826, 812, 250-th, and many others.
Yep! correct. 841 looks just like an 801, except the grid structure is
finer pitched.
>
> the sv-572 has a mu of around 160, like 811A, 572B, 808 (i think).
>
> the sv572-160 also has graphite plate (like 572b).
> and all other things equal, i have prefered metal plate tubes over
graphite,
> for some reason.
with one exception ---> 813
>
> i have not retrofit 811A into my 572-160 amp, but i'd bet it would sound
> better.
>
> the 572-160 amp is not too hard to take, though.
> in fact, it's very nice.
Agreed. I could easily convince myself that what I was hearing as not
as well defined - smooth - was in fact an artifact of the microphonics.
And perhaps to a very minor point the higher rp.
>
> > The key feature enabling the good sound was the direct
> > coupling. Tried cap coupling to the grid of the driver (exactly the
> > same quiescent point, and the driver not drawing grid current) but the
> > sound was VASTLY inferior.
> >
> not suprised.
>
> there's something fundamentally wrong with cap coupling to a A2 grid.
> the changing impedance causes rectification effects whereby the signal
> amplitude dynamically adjusts the instantaneous bias.
>
> that's got to screw with the sound, right?
Of course. However, my point was that AC coupling into the driver -
that is, the grid of the cathode follower - which never hits grid current
caused the sound to deterioriate. And moreso than I could attribute
to simply the "quality" of the capacitor.
>
> i certainly noted that in my 572-160 amp, there was a definite sweet spot
> when adjusting from zero bias up toward +25V.
>
> what was intriguing was that it occurred much earlier than i would have
> thought.
Er, yeah, I'd have to agree. I noticed it with 841 as well. Still preferred
the
higher positive bias, but the first "sweet spot" was amazingly low in
bias voltage.
>
> in other words, at zero volts, there was practically no bias, the tube was
> essentially cut-off for a big part of the audio modulation.
>
> 5V barely gave me 10 or 20mA of headroom, but the amp played loudly
> with good sound.
>
> for best linearity, my calculations said i needed about 25 to 30V,
> but the sound seemed to "bloom" at 19V.
>
> steve clued me in that these sweet spots may tend to repeat.
>
> so i revisited this experiment.
>
> above 5V we at least had listenable music, but the 1st bloom
> seemed to cut in at 16V or so, then again at 19V, then again at 22 or 23,
> and maybe again before 30V.
>
> the definite sweet spot of them all was eithe the 19V or 23V one
> (don't recall) and nothing like the predicted 28V (or whatever it was).
>
> this apparently had nothing to do with bias headroom, linearity of
operating
> point, etc. this was something else...
>
Yep. It is definitely NOT bias headroom issue. I *think*, but can not
yet prove that it has to do with DHT. See also below.
> i recently moved my sv572-160 amp to the "audition shelf"
> which sits between my speakers.
>
> and for some reason, it did not sound as good as i had recalled.
> (it has beed a few weeks since i last heard it...)
>
> i do get some vibration in to this shelf.
>
> maybe i need to damp it out....
It would be interesting to see if you notice any difference with damping.
> as noted above, the 811A has very high mu, so the gain may be
> excessive for some tastes.
Agree. If anyone is serious about 811 or 572-160 (572B) a lower gain
driver circuit would be more optimum. With ear to the speaker cone,
you can hear the noise (hiss) from the input 8532s. This was not
at all audible with the 841s in place.
>
> however, i switched to cathode drive and the sensitivity
> drops significantly. in my case, i think it's just right...
ooohh. Interesting. I would not have guessed that.
>
> another issue with these different tube types:
>
> the plate resistance of the 811A/ sv572-160 is pretty high.
> like 5 to 10K, compared to <5K for 801, 841, 572-30, 812, etc.
>
> however, on just about all of these tubes, a 10k load seems to
> work just fine.
>
> i don't seem to have a problem with a damping factor around 1...
I was expecting more overhang, perhaps not as much quickness
at the higher output Z. Just didn't happen. Possibly thats a function
of the speakers and some *need* high damping. Mine don't. Not
sure whether to classify that as good or bad :-)
>
> > Looking at the 826 specs, I'd believe that ought to work well too. Bob,
> > did you happen to try to see if that really nice feature (center tapped
> > filament) was able to buy anything?
> >
> no, i haven't.
>
> but this should be easy enough to try.
>
> i have a few small power supplies that wouldn't give me 7.5V
> at the required current, but should do 3.75V...
>
> thanks for the tip...
>
> > I'd expect to be able to pick up just
> > an extra smidgen (precise technical term) of clarity when run "parallel".
> >
> have to think about why this would be, but i don't doubt you...
If I'm right, for a constant heating power, as the filament VOLTAGE of
directly heated device is lowered (e.g. 1V 10A vs 10V 1A), there becomes
less and less of a difference between AC and DC lit filament. Sooo, with
that CT and a "real" device [yeah, you *could* test the effect with a "toy"
3V4 or equivalent], you should be able to detect an audible difference
between the filament arrangement.
[BTW, I'm not knocking 3V4s].
>
> > Please note that there's a subtle but very important distinction in the
> > kind of A2 being discussed in this thread. The IDLE voltage and most
> > of the operating range is in positive grid region. This is distinctly
> > different than what you're probably going to see with a 211, where the
> > IDLE is near zero or into negative grid region.
> >
> i agree. but i may have some conflicting observations...
>
> there is fundamentally something different between an amp with
> significant positive bias and a zero-bias amp.
>
> if you use enough positive bias, you might only rarely drive the grid
> below zero (into A1). for the most-part you stay in one quadrant.
>
> in zero bias, you (attempt to) span equally into positive and negative
> grid swings. you draw grid current only for about 1/2 the cycle.
>
> the former seems intuitively better, once you've designed the driver to go
> into grid current, you may as well stay there.
>
> i've experimented with a direct coupled design that used the grid
> as a load (no additional load resistor, the grid current was the load).
this
> seemed to be quite do-able, if i had the right
> driver tube for the job (which i didn't).
>
> a choke in parallel (essentially a choke load, that didn't take
> all of the driver dc current) seemed to make it better, though.
>
> HOWEVER, as i have found with my 833 amp, zero bias can work
> and sound just as good as "deep A2" if the driver is stupid-low
> in impedance (like 10 - 20 ohm).
Mostly agree. However, if you start straying much above that Z level,
then the fun begins. There seems to be NO magic point that is arbitrarily
apparent at or near zero bias with even modest dirver circuits. However,
until you get near the cathodes saturation point, the gain seems to
slightly increase at higher + bias. And that is offset by the greater than
zero driver impedance. In the negative bias regime, the "cutoff" starts to
lower the output tube mu (at low current and high voltage). But this is
precisely where the A1 operation gives you a slightly increased gain
in the effective driver circuit. What seems to happen is that it gives you
an extension of operation before odd order distortion overtakes even order.
Consider a 211, on the other hand. (Which I don't have any of, so can't
speak from experience, but *on paper* they look really really good!) You'll
need to bias that negatively. So the curvature starts to get you at negative
biases and as you go into positive grid region. So, the symmetrical
"limiting" starts to add more odd order products.
Or so the theory goes.
With a very low impedance driver, as you're rightly pointing out, there
is probably no penalty either way.
>
> there is still a lot of work to be done in A2.
>
Yep! Sure is.
> i got laughed at 6 years ago when i started playing with a class A2 211
> design.
>
> and i've done a lot of A2 amps using sv811-10, sv-572-10/30
> 812, etc over the years.
>
> but it wasn't til a few months ago that i found something
> that i am SURE sounds world-class.
>
> and the shared experiences of my esteemed collegues only helps to encourage
> me and excite me.
>
> thanks to steve, in particular, for spending the time to document your
> results.
>
> i hope more of you will pick up on this.
>
> it is a relatively easy way to put garden-variety transmitting tubes to
good
> use.
>
> and they look cool too!
>
> gotta run,
>
> bob.d.
>
And I'd like to add to that as well. Before I started re-examining the A2
issue,
I was SURE A2 couldn't produce as good sounding amplifier as A1, but
I was simply not correct in that assureance.
Best Regards,
Steve
=========================================================================
From: TubeGarden@aol.com
Subject: Re: [JN] 211 vs 845 vs 805
Date: Wed, 11 Jul 2001 07:05:48 EDT
Source: Sound Digest Archive v02.n923
- --part1_6b.16f78cfc.287d8d0c_boundary
Content-Type: text/plain; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
In a message dated 7/10/01 8:36:07 PM US Mountain Standard Time,
SBench@aol.com writes:
> Before I started re-examining the A2 issue,
> I was SURE A2 couldn't produce as good sounding amplifier as A1, but
> I was simply not correct in that assureance
Greets!
When I was building "Enhanced Triode Mode" circuits, thank you Tim
Pavaricini, where ever you are, using horizontal amplifiers, cheap and
plentiful, I was always in A2. Some circuits I used half of B+ for output
tube bias. I am not surprised real DH xmit triodes, not as cheap, work well
in A2 :)
Fickleness on my part caused me to move on. Not sonic quality.
Having surveyed many topologies, I am now hanging with the vacuum tube diode
bias and transformer coupling.
I am going to revisit parafeed with this beast.
Now Playing is KT88. Rp is below 900 in triode. The dynamic scale is big thru
the ehorns. Big big.
6520 is in the queue, too.
Happy Ears!
Al B^}
- --part1_6b.16f78cfc.287d8d0c_boundary
Content-Type: text/html; charset="US-ASCII"
Content-Transfer-Encoding: 7bit
<HTML><FONT FACE=arial,helvetica><BODY BGCOLOR="#ffffff"><FONT SIZE=2>In a message dated 7/10/01 8:
36:07 PM US Mountain Standard Time,
<BR>SBench@aol.com writes:
<BR>
<BR>
<BR><BLOCKQUOTE TYPE=CITE style="BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px
; PADDING-LEFT: 5px">Before I started re-examining the A2 issue,
<BR>I was SURE A2 couldn't produce as good sounding amplifier as A1, but
<BR>I was simply not correct in that assureance</FONT><FONT COLOR="#000000" SIZE=3 FAMILY="SANSSERI
F" FACE="Arial" LANG="0"></BLOCKQUOTE>
<BR></FONT><FONT COLOR="#000000" SIZE=2 FAMILY="SANSSERIF" FACE="Arial" LANG="0">
<BR>Greets!
<BR>
<BR>When I was building "Enhanced Triode Mode" circuits, thank you Tim
<BR>Pavaricini, where ever you are, using horizontal amplifiers, cheap and
<BR>plentiful, I was always in A2. Some circuits I used half of B+ for output
<BR>tube bias. I am not surprised real DH xmit triodes, not as cheap, work well
<BR>in A2 :)
<BR>
<BR>Fickleness on my part caused me to move on. Not sonic quality.
<BR>
<BR>Having surveyed many topologies, I am now hanging with the vacuum tube diode
<BR>bias and transformer coupling.
<BR>
<BR>I am going to revisit parafeed with this beast.
<BR>
<BR>Now Playing is KT88. Rp is below 900 in triode. The dynamic scale is big thru
<BR>the ehorns. Big big.
<BR>
<BR>6520 is in the queue, too.
<BR>
<BR>Happy Ears!
<BR>Al B^}
<BR>
<BR></FONT></HTML>
- --part1_6b.16f78cfc.287d8d0c_boundary--
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] 211 vs 845 vs 805
Date: Mon, 30 Jul 2001 11:42:34 -0400
Source: Sound Digest Archive v02.n936
here is some of that 845/211/826/833 thread for kevin
> ----------
> From: Danielak, Robert M
> Sent: Tuesday, July 10, 2001 7:24 PM
> To: sound@io.com; Danielak, Robert M; 'SBench@aol.com'
> Subject: RE: [JN] 211 vs 845 vs 805
>
>
>
> >
>
> Hi Bob and all,
> Agree 100%. A2 with a good driver sounds N I C E. ALL of the
> folks at the couple of auditions I had at work preferred the 841
> to the 572-160. (driver etc was the same as noted on my web pages
> on A2.).
>
> in retrospect, i see quite a few differences between these two tubes.
>
> correct me if i am wrong, but i thought the 841 is more of a medium mu
> animal (between 30 and 40).
>
> in this case it falls in line with 826, 812, 250-th, and many others.
>
> the sv-572 has a mu of around 160, like 811A, 572B, 808 (i think).
>
> the sv572-160 also has graphite plate (like 572b).
> and all other things equal, i have prefered metal plate tubes over
> graphite, for some reason.
>
> i have not retrofit 811A into my 572-160 amp, but i'd bet it would sound
> better.
>
> the 572-160 amp is not too hard to take, though.
> in fact, it's very nice.
>
> The key feature enabling the good sound was the direct
> coupling. Tried cap coupling to the grid of the driver (exactly the
> same quiescent point, and the driver not drawing grid current) but
> the
> sound was VASTLY inferior.
>
> not suprised.
>
> there's something fundamentally wrong with cap coupling to a A2 grid.
> the changing impedance causes rectification effects whereby the signal
> amplitude dynamically adjusts the instantaneous bias.
>
> that's got to screw with the sound, right?
>
> however, i have heard a cap coupled design (essentially a copy
> of eric barbour's 1st sv811-10 amp with 6sn7 driver)
> that was not half bad.
>
> for a time i pondered whether this effect could have some
> GOOD effects.
>
>
>
> Be prepared to hunt for (and find) several "sweet spots" in the
> biasing
> voltage.
>
>
> this is definitely some new ground to cover:
>
> completely ignored properties of filamentary triodes, brought to light,
> maybe...
>
> i certainly noted that in my 572-160 amp, there was a definite sweet spot
> when adjusting from zero bias up toward +25V.
>
> what was intriguing was that it occurred much earlier than i would have
> thought.
>
> in other words, at zero volts, there was practically no bias, the tube was
> essentially cut-off for a big part of the audio modulation.
>
> 5V barely gave me 10 or 20mA of headroom, but the amp played loudly
> with good sound.
>
> for best linearity, my calculations said i needed about 25 to 30V,
> but the sound seemed to "bloom" at 19V.
>
> steve clued me in that these sweet spots may tend to repeat.
>
> so i revisited this experiment.
>
> above 5V we at least had listenable music, but the 1st bloom
> seemed to cut in at 16V or so, then again at 19V, then again at 22 or 23,
> and maybe again before 30V.
>
> the definite sweet spot of them all was eithe the 19V or 23V one
> (don't recall) and nothing like the predicted 28V (or whatever it was).
>
> this apparently had nothing to do with bias headroom, linearity of
> operating point, etc. this was something else...
>
> i believe steve says it has more to do with the structure of the filament,
> itself.
>
> brilliant stuff...
>
> One big difference between the 841 and 572-160 is the microphonics.
> Tap on the 572-160 and you can hear it (which is probably why it
> didn't
> sound quite as good - acoustic feedback - not enough for oscillation
> but...).
> Tap on the 841 and nothing. 841 was dead silent: no hiss, no
> hum,
> no microphonics from the input 8532s, the driver 6n30pi or the 841s.
>
> this is very interesting.
>
> i recently moved my sv572-160 amp to the "audition shelf"
> which sits between my speakers.
>
> and for some reason, it did not sound as good as i had recalled.
> (it has beed a few weeks since i last heard it...)
>
> i do get some vibration in to this shelf.
>
> maybe i need to damp it out....
>
> Excellent imaging, quick, accurate. Did have to change the VR tubes
> a few
> times to get a good set of quiet ones, but once burnt in, no further
> issues.
>
> Was gonna try putting in a set of 809s, but didn't have a ready set
> so never
> got around to it, particularly since the 841s sound so dern good.
>
> By the way, 811s or 811As drop into the circuit just fine as Bob
> noted.
> Didn't do exhaustive tests with them, though. In hindsight, that
> might
> not be a bad idea, as soon as I get some extra time.
>
> i think just about any transmitting triode will drop in.
>
> just adjust the bias (by ear!!!).
>
> as noted above, the 811A has very high mu, so the gain may be
> excessive for some tastes.
>
> however, i switched to cathode drive and the sensitivity
> drops significantly. in my case, i think it's just right...
>
> another issue with these different tube types:
>
> the plate resistance of the 811A/ sv572-160 is pretty high.
> like 5 to 10K, compared to <5K for 801, 841, 572-30, 812, etc.
>
> however, on just about all of these tubes, a 10k load seems to
> work just fine.
>
> i don't seem to have a problem with a damping factor around 1...
>
> Looking at the 826 specs, I'd believe that ought to work well too.
> Bob,
> did you happen to try to see if that really nice feature (center
> tapped
> filament) was able to buy anything?
>
> no, i haven't.
>
> but this should be easy enough to try.
>
> i have a few small power supplies that wouldn't give me 7.5V
> at the required current, but should do 3.75V...
>
> thanks for the tip...
>
> I'd expect to be able to pick up just
> an extra smidgen (precise technical term) of clarity when run
> "parallel".
>
> have to think about why this would be, but i don't doubt you...
>
> Haven't tried Bob's transformer coupling, but I'd believe that to be
> an excellent choice too. The high gain of the 572-160 would also
> slightly relax the drive issues in that mode.
>
> yeah. even with a 10:1 step-down, it's no problem... ;)
>
> Please note that there's a subtle but very important distinction in
> the
> kind of A2 being discussed in this thread. The IDLE voltage and most
> of the operating range is in positive grid region. This is
> distinctly
> different than what you're probably going to see with a 211, where
> the
> IDLE is near zero or into negative grid region.
>
> i agree. but i may have some conflicting observations...
>
> there is fundamentally something different between an amp with
> significant positive bias and a zero-bias amp.
>
> if you use enough positive bias, you might only rarely drive the grid
> below zero (into A1). for the most-part you stay in one quadrant.
>
> in zero bias, you (attempt to) span equally into positive and negative
> grid swings. you draw grid current only for about 1/2 the cycle.
>
> the former seems intuitively better, once you've designed the driver to go
> into grid current, you may as well stay there.
>
> i've experimented with a direct coupled design that used the grid
> as a load (no additional load resistor, the grid current was the load).
> this seemed to be quite do-able, if i had the right
> driver tube for the job (which i didn't).
>
> a choke in parallel (essentially a choke load, that didn't take
> all of the driver dc current) seemed to make it better, though.
>
> HOWEVER, as i have found with my 833 amp, zero bias can work
> and sound just as good as "deep A2" if the driver is stupid-low
> in impedance (like 10 - 20 ohm).
>
> maybe it's not the same, but increasing bias to +5, +10, +15V
> did not seem to make as much difference as i would have expected.
>
> so i am still puzzled, and intrigued.
>
> there is still a lot of work to be done in A2.
>
> i got laughed at 6 years ago when i started playing with a class A2 211
> design.
>
> and i've done a lot of A2 amps using sv811-10, sv-572-10/30
> 812, etc over the years.
>
> but it wasn't til a few months ago that i found something
> that i am SURE sounds world-class.
>
> and the shared experiences of my esteemed collegues only helps to
> encourage me and excite me.
>
> thanks to steve, in particular, for spending the time to document your
> results.
>
> i hope more of you will pick up on this.
>
> it is a relatively easy way to put garden-variety transmitting tubes to
> good use.
>
> and they look cool too!
>
> gotta run,
>
> bob.d.
>
>
>
=========================================================================
From: "Danielak, Robert M" <robert.m.danielak@lmco.com>
Subject: RE: [JN] 211 vs 845 vs 805
Date: Mon, 30 Jul 2001 11:43:13 -0400
Source: Sound Digest Archive v02.n936
here's more for kevin
> ----------
> From: Danielak, Robert M
> Sent: Monday, July 09, 2001 11:09 AM
> To: sound@io.com
> Subject: RE: [JN] 211 vs 845 vs 805
>
> class A2 is not as bad as you might think.
> if you have a decent driver, it can sound very good.
>
> steve bench has done a lot of detailed study on A2 operation:
>
> http://members.aol.com/sbench/a2part1.html
>
> and he comes up with a driver that doesn't resort to transformers.
>
> i've tried both ways, and have been lucky to have a few 10:1
> step-down transformers that do the trick.
>
> i've also experimented with the 826 (thanks to gary kaufman).
>
> this was in a circuit very similar to my SE 833 amp:
>
> http://www.geocities.com/bobdanielak/se833nynoise.gif
>
> the filament voltage for the 826 is 7.5V, but i was able to
> run the 826 from 6.3VCT.
>
> i used anywhere between +10 and +25V of positive bias, with a B+
> supply of 500 to 660V.
>
> within their power limits, all of these medium mu (30 to 35)
> transmitting tubes all performed well.
>
> they seem to share a similar sonic signature, too.
>
> so the final choice can be left to visual appeal.
>
> the 826 is cute, the 812 looks like an 807 or 811A,
> the eimac 250-th is really cool, too.
>
> the 833, though, is the most radical of the lot...
>
> there are plenty more to choose from.
>
> have a blast...
>
> Hello.
>
> 866 is a mercury vapour rectifier; this one can give you about 5kV
> at a
> quarter of an amp!
>
> 811 has its fans - there is a version manufactured by Svetlana. I
> believe
> that this type is used in what is known as "Class A2", where some
> grid
> current is drawn and a driver transformer is required..
>
> From my point of view the rarity of true audio types is frustrating;
> many of
> the rf types are very attractive. As an example I have some 826s;
> these
> look superb lit up but judging by what my valve tester tells me,
> they are
> strictly class C. Grrrrrr!
>
> Best wishes
>
> Paul
> ----- Original Message -----
> From: Richard C Nevill <rnevill@is.dal.ca>
> To: Grover Gardner <groverg@postoffice.att.net>
> Cc: <sound@io.com>
> Sent: Friday, July 06, 2001 7:25 PM
> Subject: Re: [JN] 211 vs 845 vs 805
>
>
> >
> > Okay,
> >
> > Being new to this tube stuff I have a pair of RCA 811A's (
> Jeremy E.
> > didn't you want them?), a single GE DR-811 and a couple of 866's,
> one
> > globe and the other coke bottle.
> >
> > So besides the big B+'s these need are they any good as audio
> tubes?
> > Seeing in the subject 800 series tubes I thought I would ask. I
> believe I
> > read somewhere that during Desert Storm the SS radios the US was
> using had
> > problems with the sand and they dug out all their old tube stuff
> that used
> > 811's. After that no problems
> >
> > Well, cheers gang
> >
> > Richard Nevill
> >
> >
> >
> >
> >
>
>
=========================================================================
From: pderl@btinternet.com
Subject: RE: [JN] 211 vs 845 vs 805
Date: Mon, 30 Jul 2001 17:35:32 +0100 (BST)
Source: Sound Digest Archive v02.n936
Well if you want BIG I have it!
Have a look at this:
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1621486566&r=0&t=0&showTutorial=0&ed=99694520
7&indexURL=0&rd=1
Email me if you would like a picture
Paul
>
> here is some of that 845/211/826/833 thread for kevin
> > ----------
> > From: Danielak, Robert M
> > Sent: Tuesday, July 10, 2001 7:24 PM
> > To: sound@io.com; Danielak, Robert M; 'SBench@aol.com'
> > Subject: RE: [JN] 211 vs 845 vs 805
> >
> >
> >
> > >
> >
> > Hi Bob and all,
> > Agree 100%. A2 with a good driver sounds N I C E. ALL of the
> > folks at the couple of auditions I had at work preferred the 841
> > to the 572-160. (driver etc was the same as noted on my web pages
> > on A2.).
> >
> > in retrospect, i see quite a few differences between these two tubes.
> >
> > correct me if i am wrong, but i thought the 841 is more of a medium mu
> > animal (between 30 and 40).
> >
> > in this case it falls in line with 826, 812, 250-th, and many others.
> >
> > the sv-572 has a mu of around 160, like 811A, 572B, 808 (i think).
> >
> > the sv572-160 also has graphite plate (like 572b).
> > and all other things equal, i have prefered metal plate tubes over
> > graphite, for some reason.
> >
> > i have not retrofit 811A into my 572-160 amp, but i'd bet it would sound
> > better.
> >
> > the 572-160 amp is not too hard to take, though.
> > in fact, it's very nice.
> >
> > The key feature enabling the good sound was the direct
> > coupling. Tried cap coupling to the grid of the driver (exactly the
> > same quiescent point, and the driver not drawing grid current) but
> > the
> > sound was VASTLY inferior.
> >
> > not suprised.
> >
> > there's something fundamentally wrong with cap coupling to a A2 grid.
> > the changing impedance causes rectification effects whereby the signal
> > amplitude dynamically adjusts the instantaneous bias.
> >
> > that's got to screw with the sound, right?
> >
> > however, i have heard a cap coupled design (essentially a copy
> > of eric barbour's 1st sv811-10 amp with 6sn7 driver)
> > that was not half bad.
> >
> > for a time i pondered whether this effect could have some
> > GOOD effects.
> >
> >
> >
> > Be prepared to hunt for (and find) several "sweet spots" in the
> > biasing
> > voltage.
> >
> >
> > this is definitely some new ground to cover:
> >
> > completely ignored properties of filamentary triodes, brought to light,
> > maybe...
> >
> > i certainly noted that in my 572-160 amp, there was a definite sweet spot
> > when adjusting from zero bias up toward +25V.
> >
> > what was intriguing was that it occurred much earlier than i would have
> > thought.
> >
> > in other words, at zero volts, there was practically no bias, the tube was
> > essentially cut-off for a big part of the audio modulation.
> >
> > 5V barely gave me 10 or 20mA of headroom, but the amp played loudly
> > with good sound.
> >
> > for best linearity, my calculations said i needed about 25 to 30V,
> > but the sound seemed to "bloom" at 19V.
> >
> > steve clued me in that these sweet spots may tend to repeat.
> >
> > so i revisited this experiment.
> >
> > above 5V we at least had listenable music, but the 1st bloom
> > seemed to cut in at 16V or so, then again at 19V, then again at 22 or 23,
> > and maybe again before 30V.
> >
> > the definite sweet spot of them all was eithe the 19V or 23V one
> > (don't recall) and nothing like the predicted 28V (or whatever it was).
> >
> > this apparently had nothing to do with bias headroom, linearity of
> > operating point, etc. this was something else...
> >
> > i believe steve says it has more to do with the structure of the filament,
> > itself.
> >
> > brilliant stuff...
> >
> > One big difference between the 841 and 572-160 is the microphonics.
> > Tap on the 572-160 and you can hear it (which is probably why it
> > didn't
> > sound quite as good - acoustic feedback - not enough for oscillation
> > but...).
> > Tap on the 841 and nothing. 841 was dead silent: no hiss, no
> > hum,
> > no microphonics from the input 8532s, the driver 6n30pi or the 841s.
> >
> > this is very interesting.
> >
> > i recently moved my sv572-160 amp to the "audition shelf"
> > which sits between my speakers.
> >
> > and for some reason, it did not sound as good as i had recalled.
> > (it has beed a few weeks since i last heard it...)
> >
> > i do get some vibration in to this shelf.
> >
> > maybe i need to damp it out....
> >
> > Excellent imaging, quick, accurate. Did have to change the VR tubes
> > a few
> > times to get a good set of quiet ones, but once burnt in, no further
> > issues.
> >
> > Was gonna try putting in a set of 809s, but didn't have a ready set
> > so never
> > got around to it, particularly since the 841s sound so dern good.
> >
> > By the way, 811s or 811As drop into the circuit just fine as Bob
> > noted.
> > Didn't do exhaustive tests with them, though. In hindsight, that
> > might
> > not be a bad idea, as soon as I get some extra time.
> >
> > i think just about any transmitting triode will drop in.
> >
> > just adjust the bias (by ear!!!).
> >
> > as noted above, the 811A has very high mu, so the gain may be
> > excessive for some tastes.
> >
> > however, i switched to cathode drive and the sensitivity
> > drops significantly. in my case, i think it's just right...
> >
> > another issue with these different tube types:
> >
> > the plate resistance of the 811A/ sv572-160 is pretty high.
> > like 5 to 10K, compared to <5K for 801, 841, 572-30, 812, etc.
> >
> > however, on just about all of these tubes, a 10k load seems to
> > work just fine.
> >
> > i don't seem to have a problem with a damping factor around 1...
> >
> > Looking at the 826 specs, I'd believe that ought to work well too.
> > Bob,
> > did you happen to try to see if that really nice feature (center
> > tapped
> > filament) was able to buy anything?
> >
> > no, i haven't.
> >
> > but this should be easy enough to try.
> >
> > i have a few small power supplies that wouldn't give me 7.5V
> > at the required current, but should do 3.75V...
> >
> > thanks for the tip...
> >
> > I'd expect to be able to pick up just
> > an extra smidgen (precise technical term) of clarity when run
> > "parallel".
> >
> > have to think about why this would be, but i don't doubt you...
> >
> > Haven't tried Bob's transformer coupling, but I'd believe that to be
> > an excellent choice too. The high gain of the 572-160 would also
> > slightly relax the drive issues in that mode.
> >
> > yeah. even with a 10:1 step-down, it's no problem... ;)
> >
> > Please note that there's a subtle but very important distinction in
> > the
> > kind of A2 being discussed in this thread. The IDLE voltage and most
> > of the operating range is in positive grid region. This is
> > distinctly
> > different than what you're probably going to see with a 211, where
> > the
> > IDLE is near zero or into negative grid region.
> >
> > i agree. but i may have some conflicting observations...
> >
> > there is fundamentally something different between an amp with
> > significant positive bias and a zero-bias amp.
> >
> > if you use enough positive bias, you might only rarely drive the grid
> > below zero (into A1). for the most-part you stay in one quadrant.
> >
> > in zero bias, you (attempt to) span equally into positive and negative
> > grid swings. you draw grid current only for about 1/2 the cycle.
> >
> > the former seems intuitively better, once you've designed the driver to go
> > into grid current, you may as well stay there.
> >
> > i've experimented with a direct coupled design that used the grid
> > as a load (no additional load resistor, the grid current was the load).
> > this seemed to be quite do-able, if i had the right
> > driver tube for the job (which i didn't).
> >
> > a choke in parallel (essentially a choke load, that didn't take
> > all of the driver dc current) seemed to make it better, though.
> >
> > HOWEVER, as i have found with my 833 amp, zero bias can work
> > and sound just as good as "deep A2" if the driver is stupid-low
> > in impedance (like 10 - 20 ohm).
> >
> > maybe it's not the same, but increasing bias to +5, +10, +15V
> > did not seem to make as much difference as i would have expected.
> >
> > so i am still puzzled, and intrigued.
> >
> > there is still a lot of work to be done in A2.
> >
> > i got laughed at 6 years ago when i started playing with a class A2 211
> > design.
> >
> > and i've done a lot of A2 amps using sv811-10, sv-572-10/30
> > 812, etc over the years.
> >
> > but it wasn't til a few months ago that i found something
> > that i am SURE sounds world-class.
> >
> > and the shared experiences of my esteemed collegues only helps to
> > encourage me and excite me.
> >
> > thanks to steve, in particular, for spending the time to document your
> > results.
> >
> > i hope more of you will pick up on this.
> >
> > it is a relatively easy way to put garden-variety transmitting tubes to
> > good use.
> >
> > and they look cool too!
> >
> > gotta run,
> >
> > bob.d.
> >
> >
> >
=========================================================================
From: Steve Van Osdell <svanos@queencity.com>
Subject: [JN] 247A WE tubes
Date: Sat, 12 Aug 2000 12:55:54 -0400
Source: Sound Digest Archive v02.n625
I've also got a pair of 247A tubes up on ebay (I think they are equal to
one side of a 12AX7). If anybody wants them, I can stop the auction
because reserve isn't met yet. Are they worth $130 for the pair? NOS
in box.
Thanks, Steve
=========================================================================
From: "BobC" <bobcx@bellatlantic.net>
Subject: Re: [JN] 247A WE tubes
Date: Sat, 12 Aug 2000 13:38:57 -0400
Source: Sound Digest Archive v02.n625
> If anybody wants them, I can stop the auction
> because reserve isn't met yet. Are they worth $130 for the pair? NOS
> in box.
I believe the reserve isn't met yet because nobody has bid on them.
BC
=========================================================================
From: tube@jump.net
Subject: Re: [JN] 247A WE tubes
Date: Sat, 12 Aug 2000 15:44:27 -0500
Source: Sound Digest Archive v02.n625
"Paul@13E1.com" wrote:
> Perhaps what Bob meant to say is that they are not worth $130.
>
> A whole 12AX7 certainly is not, so I doubt that half of one could be!!
Actually, I think he was referring to the extremely unlikely possibility of
a reserve being met WITHOUT any bidding!
I got a good laugh out of it, whatever he was doing ...
Phil
> >
> > > If anybody wants them, I can stop the auction
> > > because reserve isn't met yet. Are they worth $130 for the pair? NOS
> > > in box.
> >
> > I believe the reserve isn't met yet because nobody has bid on them.
> >
> > BC
> >
> >
=========================================================================
From: Steve Van Osdell <svanos@queencity.com>
Subject: Re: [JN] 247A WE tubes
Date: Sat, 12 Aug 2000 18:22:18 -0400
Source: Sound Digest Archive v02.n625
Well, first, I was only going by what another person (who should know) told
me. And I have seen whole NOS Telefunken 12AX7's going for $60 or more. So,
I'm open to more expert opinion about their value (hopefully without sarcasm).
Thanks, Steve
"Paul@13E1.com" wrote:
> Perhaps what Bob meant to say is that they are not worth $130.
>
> A whole 12AX7 certainly is not, so I doubt that half of one could be!!
>
> Paul Leclercq [function before fashion :-)]
> ----- Original Message -----
> From: BobC <bobcx@bellatlantic.net>
> To: Joe List <sound@lists.io.com>
> Sent: Saturday, August 12, 2000 6:38 PM
> Subject: Re: [JN] 247A WE tubes
>
> >
> >
> > > If anybody wants them, I can stop the auction
> > > because reserve isn't met yet. Are they worth $130 for the pair? NOS
> > > in box.
> >
> > I believe the reserve isn't met yet because nobody has bid on them.
> >
> > BC
> >
> >
=========================================================================
From: Steve Van Osdell <svanos@queencity.com>
Subject: Re: [JN] 247A WE tubes
Date: Sat, 12 Aug 2000 18:25:37 -0400
Source: Sound Digest Archive v02.n625
Bob,
I think the accuracy of the statement 'reserve isn't met' holds true whether
someone has bid or not, or am I mistaken? Are you always this good with
stating oxymorons?
Steve
BobC wrote:
> > If anybody wants them, I can stop the auction
> > because reserve isn't met yet. Are they worth $130 for the pair? NOS
> > in box.
>
> I believe the reserve isn't met yet because nobody has bid on them.
>
> BC
=========================================================================
From: "Paul@13E1.com" <triode@bow-tie.org.uk>
Subject: Re: [JN] 247A WE tubes
Date: Sat, 12 Aug 2000 20:53:43 +0100
Source: Sound Digest Archive v02.n625
Perhaps what Bob meant to say is that they are not worth $130.
A whole 12AX7 certainly is not, so I doubt that half of one could be!!
Paul Leclercq [function before fashion :-)]
- ----- Original Message -----
From: BobC <bobcx@bellatlantic.net>
To: Joe List <sound@lists.io.com>
Sent: Saturday, August 12, 2000 6:38 PM
Subject: Re: [JN] 247A WE tubes
>
>
> > If anybody wants them, I can stop the auction
> > because reserve isn't met yet. Are they worth $130 for the pair? NOS
> > in box.
>
> I believe the reserve isn't met yet because nobody has bid on them.
>
> BC
>
>
=========================================================================
From: "Fred Volz" <fcv@emotiveaudio.com>
Subject: Re: [JN] 247A WE tubes
Date: Mon, 14 Aug 2000 09:12:47 -0400
Source: Sound Digest Archive v02.n627
- -----Original Message-----
From: David Crittle <retrovox@bigpond.com>
To: sound@lists.io.com <sound@lists.io.com>
Date: Monday, August 14, 2000 8:16 AM
Subject: Re: [JN] 247A WE tubes
>half a 12AX7? Isn't that a 6AV6?
>
>David
>
>
According to my tube book, a 6AV6 is a dual diode/triode. If I look up
12AX7, it says to reference 6AV6s triode section for the curves and
characteristics. But, the 6AV6 has a max plate dissipation rating of 0.55
Watts while the 12AX7 has a 1.2 Watt rating per section. So, it seems that,
while the curves and characteristics are similar, they are not really the
same triode.
It would be interesting, however, to listen to each of these in a circuit
suitably designed to use either tube. 6AV6s cost only half as much as 12AX7s
on a per triode basis.
Fred Volz
fcv@emotiveaudio.com
=========================================================================
From: David Crittle <retrovox@bigpond.com>
Subject: Re: [JN] 247A WE tubes
Date: Mon, 14 Aug 2000 21:33:27 +1000
Source: Sound Digest Archive v02.n627
>Well, first, I was only going by what another person (who should know) told
>me. And I have seen whole NOS Telefunken 12AX7's going for $60 or more. So,
>I'm open to more expert opinion about their value (hopefully without sarcasm).
half a 12AX7? Isn't that a 6AV6?
David
=========================================================================
From: Simon Busbridge <S.C.Busbridge@bton.ac.uk>
Subject: Re: [JN] RE: 24V rms AC is 68V peak-peak, right?
Date: Thu, 12 Apr 2001 08:11:07 +0100 (BST)
Source: Sound Digest Archive v02.n865
Only if the currents taken from the + and the - supplies are balanced.
Otherwise the 'false earth' will waft up or down to one or other of the
supplies. You will be relying of charge balancing between the two
capacitors to maintain your earth point. Better to use a centre tap.
Simon
Simon Busbridge, BSc(Hons) PhD CPhys MInstP
School of Engineering
University of Brighton
Lewes Road
Moulsecoomb
Brighton BN2 4GJ
UNITED KINGDOM
Tel: 0044 (0)1273 642542
Fax: 0044 (0)1273 642327/642301
e-mail: s.c.busbridge@bton.ac.uk, scbusbridge@hotmail.com
On Thu, 12 Apr 2001, Sellek, Grant (TSA) wrote:
> Thanks to all those who replied, I certainly gave up the idea
> of getting +- 33V rails from a single 24V rms secondary.
> I need a 48V rms centre tapped supply, or a pair of 24V rms.
>
> Now I have to hand a TX with a 46V rms secondary, which is near
> enough to the 48V rms I desire, especially as the mains supply
> is consistently a bit high at my house. But it has no centre
> tap. Is this an impediment?
>
> I can see no reason against hooking up the 46V secondary, full
> bridge the output to get approx 64V DC, floating. Span this
> with a pair of series capacitances, and anchor the midpoint to
> earth. This will give me near to +32V and -32V rails, with the
> centre point earthed. So there seems top be no problem with a
> floating secondary winding -- correct?
>
> Grant
>
> Grant Sellek, Adelaide, Australia
>
=========================================================================
From: "Sellek, Grant (TSA)" <Grant.Sellek@transport.sa.gov.au>
Subject: [JN] RE: 24V rms AC is 68V peak-peak, right?
Date: Thu, 12 Apr 2001 16:20:20 +0930
Source: Sound Digest Archive v02.n865
Thanks to all those who replied, I certainly gave up the idea
of getting +- 33V rails from a single 24V rms secondary.
I need a 48V rms centre tapped supply, or a pair of 24V rms.
Now I have to hand a TX with a 46V rms secondary, which is near
enough to the 48V rms I desire, especially as the mains supply
is consistently a bit high at my house. But it has no centre
tap. Is this an impediment?
I can see no reason against hooking up the 46V secondary, full
bridge the output to get approx 64V DC, floating. Span this
with a pair of series capacitances, and anchor the midpoint to
earth. This will give me near to +32V and -32V rails, with the
centre point earthed. So there seems top be no problem with a
floating secondary winding -- correct?
Grant
Grant Sellek, Adelaide, Australia
=========================================================================
From: alan cameron <alan@thehub.com.au>
Subject: [JN] 25W pots for Oz-Joes
Date: Wed, 3 Nov 1999 18:34:43 +1000
Source: Sound Digest Archive v02.n320
hi Oz-Joes,
the other day I came across a few 5k 25W wire-wound pots, NIB. Just the
thing for the cathode resistor of your 2A3 direct coupled amp. If an OzJoe
wasnts a couple, let me know and I'll go and get them (if they're still
there).
Dunno, how does something like ten bucks each sound.
My email is very dodgy at he moment; phone on 0408 441 277 might work best.
alan
still lurking
=========================================================================
From: =?iso-8859-1?q?Josef=20Aigner?= <josef_aigner@yahoo.com>
Subject: Re: [JN] 26/45 amp. Schematic?
Date: Fri, 14 Jan 2000 15:01:11 -0800 (PST)
Source: Sound Digest Archive v02.n404
Don,
on monday, I have to scan the drawing since I have no software to do
this (does somebody know a kind of shareware etc. ?).
Josef
__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
http://im.yahoo.com
=========================================================================
From: =?iso-8859-1?q?Josef=20Aigner?= <josef_aigner@yahoo.com>
Subject: Re: [JN] 26/45 amp. was: Choke connection
Date: Fri, 14 Jan 2000 06:33:36 -0800 (PST)
Source: Sound Digest Archive v02.n402
Hi Don,
mine is also for a edgarhorn D54/Fostex 925 setup....
josef
__________________________________________________
Do You Yahoo!?
Talk to your friends online with Yahoo! Messenger.
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=========================================================================
From: "Carter Hendricks" <carter@i1.net>
Subject: [JN] 26-46 amp
Date: Sun, 22 Oct 2000 22:40:11 -0500
Source: Sound Digest Archive v02.n704
I'm admittedly behind on my reports on class [list] projects.
I'll wait a while longer before talking about the 46 PP amp.
I plan to try a different driver. But I finished another amp,
and this one makes me happy.
The amp is a 26, direct coupled to a 46.
The idea is from Shishido, who used it several times as a
driver for his serious A2 amps. I've built with 26 and with
46 and they are wonderful tubes.
First: this is a 1.25 watt amp. It will not play symphonic
music or heavy metal. It won't play loud.
But, as JL says, it's 1,250 mW. It will play small group
jazz and classical. It plays too loud to talk.
The 46 is run at the standard operating point, 250 volts
plate, 33 vgk, 22 mA. To make the direct coupling work,
the 46 cathode is elevated to ~ 125 v. [Raw supply is
raised to ~345 volts]. The cathode resistance is two
3k Mills in series, each resistor bypassed by a 100uF
100v Muse cap. There is a 56k dropping resistor to
a 33k Mills plate resistor for the 26, and I used a fat
2.5k CC cathode resistor bypassed by a pair of 50uF
green Muse caps in parallel.
The 26 doesn't have enough voltage gain to drive the 46
to full glory. I always use a line stage [right now my 42]
but sometimes borrow a CD player or phono stage. So
I picked up some extra gain with an A18 step up as an
input transformer. [Shishido also used input trannies].
I used a 100k AB pot as a load and volume control.
The OPT is the Black Art 417A transformer. It is set up
for just 20 mA. It would be fun to try running the 46 like
a 45, but not with these OPT's. I prefer 26's at a lower
voltage / higher current, but input headroom looked
tight.
The 26 [and 46] are direct heated. The 26 sounds best
humming along on AC [you can get used to it] but sounds
almost as good on current regulation. I used a 6.3 x2 mil
spec filament transformer, schottkeys, ferrite beads, and
a cap and LT1085 to make a raw DC supply to feed the
current regulator, which I mounted [with isolation washers
& gasket] next to each 26. I used [.5 & .7] 5 watt Mills for
the series current set resistors. The 46 just uses an AB
50 ohm balance pot, which I'll parallel with a couple 25 ohm
CC's.
The power supply uses a MQ transformer and filter choke
in an LC. I use a "Gordon" ~.7 film cap before the choke,
to adjust the voltage and knock down the uglies. I use
beads on the input of the first, 56uF switch grade filter cap.
I use more beads and a small amount of resistance before
more filter caps [~150uF] and another small R before
another 56uF close to the OPT. A small amount of noise can be heard with my
ear at each speaker, but I usually
don't listen that way. Anna helped me set the hum pots!
Amp design is a balance of compromises. On this amp
[with a 14 inch square chassis] I wanted to try a quick, fast
power supply structure. Shishido was quoted somewhere
that he wasn't interested in old tube sound, he wanted modern sound. I
think his circuit and this power supply accomplish a clear musical sound.
I've been listening to the amp through a borrowed phono
stage and a borrowed Exposure CD player. Both sound
better driven through the choke-loaded 42 line stage. I'm
using my Diatones in 2 cu ft boxes.
The amp is fast and lively. I've been listening to some small
group Benny Carter jazz while writing this. The strength of the amp is in
the clarity of the sax, in pitch, dynamics, and metal tone. BC plays loud,
plays soft, and it is all coming through. I keep stopping my writing to
listen to Benny Carter.
The strengths of a small amp cut both ways. There is great
clarity and focus, not in the Charlie Bergan way but in the
sense of concentration, of a direct coupling to the music.
But this clarity means that each selection in material, layout
and circuit is irrevocably part of the design, is part of the music. I know
what a cheap [Hammond] filt