The Potato Amp?
John Byrns
Hi Andre,
Please forgive me if I have asked this question before, but how did your
Potato Amp come by its name?
Regards,
John Byrns
Surf my web pages at, http://users.rcn.com/jbyrns/
Andre Jute
John Byrns wrote:
> Hi Andre,
>
> Please forgive me if I have asked this question before, but how did your
> Potato Amp come by its name?
Potato Amp is not the amp's name; it merely describes a single-tube
amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
I don't know who first made the pun. I heard it first from Dan
Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
consideration whether an amp built with two tubes in one envelope (per
channel) is still a potato amp. An example would be Dan's Single-Ended
Experimenter's or SEX; I had a sidebar in my original review for Glass
Audio of the SEX amp on the lexicography of potato amps but the editor
preferred to give the sidebar space to an advertisement...
> Regards,
>
> John Byrns
>
> Surf my web pages at, http://users.rcn.com/jbyrns/
HTH.
Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
Robert Morein
>
> John Byrns wrote:
>> Hi Andre,
>>
>> Please forgive me if I have asked this question before, but how did your
>> Potato Amp come by its name?
>
> Potato Amp is not the amp's name; it merely describes a single-tube
> amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
> I don't know who first made the pun. I heard it first from Dan
> Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
> Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
> consideration whether an amp built with two tubes in one envelope (per
> channel) is still a potato amp. An example would be Dan's Single-Ended
> Experimenter's or SEX; I had a sidebar in my original review for Glass
> Audio of the SEX amp on the lexicography of potato amps but the editor
> preferred to give the sidebar space to an advertisement...
>
>> Regards,
>>
>> John Byrns
>>
>> Surf my web pages at, http://users.rcn.com/jbyrns/
>
> HTH.
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
"a collection of sockpuppeting vermillistude"
Robert Morein Failed Human
Pooh Bear
Andre Jute wrote:
> John Byrns wrote:
> > Hi Andre,
> >
> > Please forgive me if I have asked this question before, but how did your
> > Potato Amp come by its name?
>
> Potato Amp is not the amp's name; it merely describes a single-tube
> amp.
Nah. it's well know it's simply an amp suitable for Mr Potatohead types.
Graham
Iain Churches
"Pooh Bear" <rabbitsfriend...@hotmail.com> wrote in message
news:43FE973C...@hotmail.com...
Morning Graham.
In the late 1920's and 30's, Paul Whiteman was the most popular
band leader in the USA. Few people know of him these days.
Suffice to say, he was important enough for George Gershwin
to dedicate "Rhapsody in Blue" to the Whiteman Orchestra,
of which both the legendary Bix Beiderbecke and singer
Bing Crosby were members
He was known affectionately among musicians as Potato Head.
Probably he listened to his own music on a single-tube amp.
Iain
Arny Krueger
news:dtmbt7$bat$1...@phys-news4.kolumbus.fi
> In the late 1920's and 30's, Paul Whiteman was the most
> popular band leader in the USA. Few people know of him these
> days.
> Suffice to say, he was important enough for George
> Gershwin to dedicate "Rhapsody in Blue" to the Whiteman Orchestra,
> of which both the legendary Bix Beiderbecke and singer
> Bing Crosby were members
> He was known affectionately among musicians as Potato
> Head.
> Probably he listened to his own music on a single-tube
> amp.
Yes, a single tube amp as in 5-tube AC-DC radio. In the days of tubes
*everybody* had one stashed away someplace and listened to it at least
occasionally, but only as a matter of convenience.
Probably, Mr. Whiteman listened to his own music on a push-pull amp whenever
he could. In the days of, tubed amps with push-pull output stages and
negative feedback were a sign of good taste.
Iain Churches
"Arny Krueger" <ar...@hotpop.com> wrote in message
news:CeWdnUQF1bcie2Pe...@comcast.com...
Mike Gilmour
Paul Whiteman was very popular indeed, also widely known amongst the public
at that time as the 'King of Jazz', he was certainly idolised by the Duke.
> Probably he listened to his own music on a single-tube amp.
Oh course :o)
>
> Iain
>
>
>
Iain Churches
"Mike Gilmour" <mi...@tfjazz.freeserve.co.uk> wrote in message
news:pI2dndRmk95HdGPe...@pipex.net...
The King of Jazz was a bit of a misnomer.
His orchestra did not really play jazz
although he did have some very good jazz players.
But people were still trying to work out was jazz (written "jass"
in those days) was all about.
>
>> Probably he listened to his own music on a single-tube amp.
>
> Oh course :o)
:-)))
Mike Gilmour
That monika was more to do with his own very blantant self-promotion than
anything else, e.g. see the 1930 Universal film 'King of Jazz' were Paul
played the lead. I agree his orchestra didn't play much jazz but it was the
name he was known as back then and it stuck (unfortunately), mainly because
he paid his muso's extremely well so no one was going to argue about his
title :-) back to single-toobas now...
Arny Krueger
> "Arny Krueger" <ar...@hotpop.com> wrote in message
> news:CeWdnUQF1bcie2Pe...@comcast.com...
>> "Iain Churches" <taelN...@kolumbus.fi> wrote in message
>> news:dtmbt7$bat$1...@phys-news4.kolumbus.fi
>>> In the late 1920's and 30's, Paul Whiteman was the most
>>> popular band leader in the USA. Few people know of him
>>> these days.
I must be among the few.
>>> Suffice to say, he was important enough for George
>>> Gershwin to dedicate "Rhapsody in Blue" to the Whiteman
>>> Orchestra, of which both the legendary Bix Beiderbecke
>>> and singer Bing Crosby were members
Still fixtures in the 40s and 50s.
>>> He was known affectionately among musicians as Potato
>>> Head.
>>> Probably he listened to his own music on a single-tube
>>> amp.
>> Yes, a single tube amp as in 5-tube AC-DC radio. In the
>> days of tubes *everybody* had one stashed away someplace
>> and listened to it at least occasionally, but only as a
>> matter of convenience.
>> Probably, Mr. Whiteman listened to his own music on a
>> push-pull amp whenever he could. In the days of, tubed
>> amps with push-pull output stages and negative feedback
>> were a sign of good taste.
> Unfortunately the time frame does not fit.
As usual Iain, you're talking out the back of your neck. Paul Whiteman the
band leader died in 1967, if any of the standard biographies are to
believed. Push-pull amplification dates back to 1927.
If you were familiar with the schematic of higher end radios and audio
systems back in the 30s, 40s and 50s, you'd know that push-pull
amplification was characteristic of just about anything with pretentions to
quality.
John Byrns
Jute" <fiu...@yahoo.com> wrote:
> John Byrns wrote:
> > Hi Andre,
> >
> > Please forgive me if I have asked this question before, but how did your
> > Potato Amp come by its name?
>
> Potato Amp is not the amp's name; it merely describes a single-tube
> amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
> I don't know who first made the pun. I heard it first from Dan
> Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
> Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
> consideration whether an amp built with two tubes in one envelope (per
> channel) is still a potato amp. An example would be Dan's Single-Ended
> Experimenter's or SEX; I had a sidebar in my original review for Glass
> Audio of the SEX amp on the lexicography of potato amps but the editor
> preferred to give the sidebar space to an advertisement...
Hi Andre,
Thanks for explaining the meaning of a "potato" amp so that it could
penetrate my occasionally thick skull.
I would consider "an amp built with two tubes in one envelope" to fit this
definition, in fact I am sort of fascinated by the idea of push pull
"potato" amp using a transformer for phase inversion. Do you know of any
suitable dual triodes, something roughly on the order of two 417s in a
single envelope?
Andre Jute
Tomorrow I'll probably regret answering this now as I am wiped. The
twin-triode Dan chose for the SEX, the 6DN7 is two dissimilar tubes in
the same octal envelope, so it won't do.
The tube that comes automatically to mind is 6AS7 but that isn't
anything like a 417A.
I assume the reasons you choose the 417A must include one or more of
the following:
1. High gain
2. Works direct out of CD (2V signal peak is good)
3. Decent current capability.
Steve Bench built an amp with a bank of 417A but I can't now remember
whether it was PSE or PP.
Tell us more of your parameters. Where would the signal come from, can
your IST be a step up as well as splitter, how much power do you want?
There was a Russian just on RAT, advertising tubes. He sells only
wholesale, I think, but he reminded me of the 6P45S (and similar
numbers -- there is no agreed transliteration of cyrillic tube
nomenclature; try 6pi45C or S too) which is a very beefy little tube,
more like the 417's big but rare and expensive brother the 437A or
167M, but also only a single triode in the envelope.
I'm waffling. I'll hit the books when I wake up.
Andre Jute
Iain Churches
>> The King of Jazz was a bit of a misnomer.
>> His orchestra did not really play jazz
>> although he did have some very good jazz players.
>>
>> But people were still trying to work out was jazz (written "jass"
>> in those days) was all about.
>
>
> That monika was more to do with his own very blantant self-promotion than
> anything else, e.g. see the 1930 Universal film 'King of Jazz' were Paul
> played the lead. I agree his orchestra didn't play much jazz but it was
> the name he was known as back then and it stuck (unfortunately), mainly
> because he paid his muso's extremely well so no one was going to argue
> about his title :-) back to single-toobas now...
There was also a string section of 6 (and sometimes eight) violins.
Not really a jazz , more like variety orchestra. The Billy Cotton
Band Show comes to mind:-)
Iain
John Stewart
A 6DZ7 would do it. It has a pair of 6BQ5's inside one bottle. Run them triode
or pentode, your choice. Each section triode mu = 19 while G is about 12
ma/volt.
Cheers, John Stewart
Iain Churches
> "Iain Churches" <taelN...@kolumbus.fi> wrote in message
> news:dtmpbu$gag$1...@phys-news4.kolumbus.fi
>> "Arny Krueger" <ar...@hotpop.com> wrote in message
>> news:CeWdnUQF1bcie2Pe...@comcast.com...
>>> "Iain Churches" <taelN...@kolumbus.fi> wrote in message
>>> news:dtmbt7$bat$1...@phys-news4.kolumbus.fi
>
>>>> In the late 1920's and 30's, Paul Whiteman was the most
>>>> popular band leader in the USA. Few people know of him
>>>> these days.
>
> I must be among the few.
>
>>>> Suffice to say, he was important enough for George
>>>> Gershwin to dedicate "Rhapsody in Blue" to the Whiteman
>>>> Orchestra, of which both the legendary Bix Beiderbecke
>>>> and singer Bing Crosby were members
>
> Still fixtures in the 40s and 50s.
Totally incorrect. Bix died in aged 28 in 1931,
Crosby left Paul Whiteman soon afterwards.
> Paul Whiteman the
> band leader died in 1967, if any of the standard biographies are to
> believed. Push-pull amplification dates back to 1927.
Your date for Whiteman's death is correct, but according to his biography,
he made few appearances after the early thirties. So, perhaps just
about push pull.
But I still like to think of him with the single tube
"potato amp" which Andre describes:-))
Iain
John Stewart
John Byrns
Jute" <fiu...@yahoo.com> wrote:
> John Byrns wrote:
> > In article <1140717246....@t39g2000cwt.googlegroups.com>, "Andre
> > Jute" <fiu...@yahoo.com> wrote:
> > > John Byrns wrote:
> > > >
> > > > Please forgive me if I have asked this question before, but how did your
> > > > Potato Amp come by its name?
> > >
> > > Potato Amp is not the amp's name; it merely describes a single-tube
> > > amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
> > > I don't know who first made the pun. I heard it first from Dan
> > > Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
> > > Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
> > > consideration whether an amp built with two tubes in one envelope (per
> > > channel) is still a potato amp. An example would be Dan's Single-Ended
> > > Experimenter's or SEX; I had a sidebar in my original review for Glass
> > > Audio of the SEX amp on the lexicography of potato amps but the editor
> > > preferred to give the sidebar space to an advertisement...
> >
> > Thanks for explaining the meaning of a "potato" amp so that it could
> > penetrate my occasionally thick skull.
> >
> > I would consider "an amp built with two tubes in one envelope" to fit this
> > definition, in fact I am sort of fascinated by the idea of push pull
> > "potato" amp using a transformer for phase inversion. Do you know of any
> > suitable dual triodes, something roughly on the order of two 417s in a
> > single envelope?
>
> Tomorrow I'll probably regret answering this now as I am wiped. The
> twin-triode Dan chose for the SEX, the 6DN7 is two dissimilar tubes in
> the same octal envelope, so it won't do.
>
> The tube that comes automatically to mind is 6AS7 but that isn't
> anything like a 417A.
>
> I assume the reasons you choose the 417A must include one or more of
> the following:
>
> 1. High gain
>
> 2. Works direct out of CD (2V signal peak is good)
>
> 3. Decent current capability.
>
> Steve Bench built an amp with a bank of 417A but I can't now remember
> whether it was PSE or PP.
>
> Tell us more of your parameters. Where would the signal come from, can
> your IST be a step up as well as splitter, how much power do you want?
Hi Andre,
While the 417A doesn't particularly stir my audio passions, I am starting
with your SE 417A "potato" amplifier as the baseline. From my perspective
the specifications of an ideal push pull "potato" amplifier would be a
maximum output of 2 Watts, which could be driven to a 1 Watt output with
the 2 volt peak signal from a CD player that you quote.
The input transformer can have a voltage step up, the transformer I have
in mind has a voltage step up from the primary of 3X grid to grid.
I have in mind some sort of dual triode tube with an anode resistance some
where in the neighborhood of 1,700 Ohms, a transconductance as high as
possible, and an anode dissipation rating sufficient to provide a 2 Watt
output.
Any thoughts?
John Byrns
> John Byrns wrote:
> > In article <1140717246....@t39g2000cwt.googlegroups.com>, "Andre
> > Jute" <fiu...@yahoo.com> wrote:
> > > John Byrns wrote:
> > > >
> > > > Please forgive me if I have asked this question before, but how did your
> > > > Potato Amp come by its name?
> > >
> > > Potato Amp is not the amp's name; it merely describes a single-tube
> > > amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
> > > I don't know who first made the pun. I heard it first from Dan
> > > Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
> > > Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
> > > consideration whether an amp built with two tubes in one envelope (per
> > > channel) is still a potato amp. An example would be Dan's Single-Ended
> > > Experimenter's or SEX; I had a sidebar in my original review for Glass
> > > Audio of the SEX amp on the lexicography of potato amps but the editor
> > > preferred to give the sidebar space to an advertisement...
> >
> > Thanks for explaining the meaning of a "potato" amp so that it could
> > penetrate my occasionally thick skull.
> >
> > I would consider "an amp built with two tubes in one envelope" to fit this
> > definition, in fact I am sort of fascinated by the idea of push pull
> > "potato" amp using a transformer for phase inversion. Do you know of any
> > suitable dual triodes, something roughly on the order of two 417s in a
> > single envelope?
>
> A 6DZ7 would do it. It has a pair of 6BQ5's inside one bottle. Run them triode
> or pentode, your choice. Each section triode mu = 19 while G is about 12
> ma/volt.
Hi John,
I used to have some 6DZ7s, but I sold them to someone who needed them to
use in a commercial amplifier they owned.
The 6DZ7 doesn't really work in a "potato" amplifier because both screen
grids share a common base pin, so the tube can't be used in a single tube
push pull triode amplifier, besides I would like to use real triodes.
Without triode mode available, a small amount of cathode feedback would be
needed to lower the output resistance, but IIRC the 6DZ7 also has only a
single cathode pin.
Andre Jute
I can't think of anything like you want.
What comes to my mind instead is the 6SN7GTB which will give you near
enough one watt of very clean power in PP.
Andre Jute
Iain Churches
> "Iain Churches" <taelN...@kolumbus.fi> wrote in message
> news:dtmpbu$gag$1...@phys-news4.kolumbus.fi
>> "Arny Krueger" <ar...@hotpop.com> wrote in message
>> news:CeWdnUQF1bcie2Pe...@comcast.com...
>>> "Iain Churches" <taelN...@kolumbus.fi> wrote in message
>>> news:dtmbt7$bat$1...@phys-news4.kolumbus.fi
>
>>>> In the late 1920's and 30's, Paul Whiteman was the most
>>>> popular band leader in the USA. Few people know of him
>>>> these days.
>
> I must be among the few.
>
Good Morning Arny. Do you also know of the more modern
recordings of The New Paul Whiteman Orchestra, under the
direction of Alan Cohen?
When cornettist and author Dick Sudhalter was doing research
for his biography on Bix, he came across the set of scores and
parts used by Whiteman that had been collecting dust in a
museum for nearly two generations.
He got permission to borrow them, and brought them to London,
for new recordings. The parts still had the original pencil markings
written by the players, including some by Bix. Fascinating to see,
and wonderful to hear performed:-)
Iain
Ruud Broens
"Andre Jute" <fiu...@yahoo.com> wrote in message
news:1141000733.8...@z34g2000cwc.googlegroups.com...
:
: John Byrns wrote:
: > In article <1140933911....@p10g2000cwp.googlegroups.com>, "Andre
: > Jute" <fiu...@yahoo.com> wrote:
:
: > Hi Andre,
: >
: > While the 417A doesn't particularly stir my audio passions, I am starting
: > with your SE 417A "potato" amplifier as the baseline. From my perspective
: > the specifications of an ideal push pull "potato" amplifier would be a
: > maximum output of 2 Watts, which could be driven to a 1 Watt output with
: > the 2 volt peak signal from a CD player that you quote.
: >
: > The input transformer can have a voltage step up, the transformer I have
: > in mind has a voltage step up from the primary of 3X grid to grid.
: >
: > I have in mind some sort of dual triode tube with an anode resistance some
: > where in the neighborhood of 1,700 Ohms, a transconductance as high as
: > possible, and an anode dissipation rating sufficient to provide a 2 Watt
: > output.
: >
: > Any thoughts?
: >
: >
: > Regards,
: >
: > John Byrns
: >
: >
: > Surf my web pages at, http://users.rcn.com/jbyrns/
:
: I can't think of anything like you want.
:
: What comes to my mind instead is the 6SN7GTB which will give you near
: enough one watt of very clean power in PP.
:
: Andre Jute
It could be done with a JJ ECC99, with a balancing step-up tranny
about 2W possible in PP (each Pa=5W, close to the 6BX7)
with 2Vtt input upped to 12 Vtt.
Rudy
Ruud Broens
"Ruud Broens" <bro...@wanadoo.nl> wrote in message
news:4403577c$0$92924$dbd4...@news.wanadoo.nl...
: It could be done with a JJ ECC99, with a balancing step-up tranny
: about 2W possible in PP (each Pa=5W, close to the 6BX7)
: with 2Vtt input upped to 12 Vtt.
:
: Rudy
err, per tube, that would be 12 times step up. hmmm.
you'd want something like this, but reversed:
http://www.cinemag.biz/direct_box/CM-DBX.pdf
;-)
R.
John Byrns
Jute" <fiu...@yahoo.com> wrote:
> John Byrns wrote:
> > In article <1140933911....@p10g2000cwp.googlegroups.com>, "Andre
> > Jute" <fiu...@yahoo.com> wrote:
> >
> > > Tell us more of your parameters. Where would the signal come from, can
> > > your IST be a step up as well as splitter, how much power do you want?
> >
> > While the 417A doesn't particularly stir my audio passions, I am starting
> > with your SE 417A "potato" amplifier as the baseline. From my perspective
> > the specifications of an ideal push pull "potato" amplifier would be a
> > maximum output of 2 Watts, which could be driven to a 1 Watt output with
> > the 2 volt peak signal from a CD player that you quote.
> >
> > The input transformer can have a voltage step up, the transformer I have
> > in mind has a voltage step up from the primary of 3X grid to grid.
> >
> > I have in mind some sort of dual triode tube with an anode resistance some
> > where in the neighborhood of 1,700 Ohms, a transconductance as high as
> > possible, and an anode dissipation rating sufficient to provide a 2 Watt
> > output.
> >
> > Any thoughts?
>
> I can't think of anything like you want.
>
> What comes to my mind instead is the 6SN7GTB which will give you near
> enough one watt of very clean power in PP.
Hi Andre,
The 6SN7GTB has too high a plate resistance and the transconductance is
too low for the "potato" amplifier design I am thinking of.
Actually the 7044 tube that you mentioned in another thread comes pretty
close to what I am looking for, its main shortcoming being an inadequate
anode dissipation rating.
Sander deWaal
>The 6SN7GTB has too high a plate resistance and the transconductance is
>too low for the "potato" amplifier design I am thinking of.
6BX7?
Or the Russian 6C19 pi?
http://home.planet.nl/~benadski/CO/6S19P.pdf
--
- Never argue with idiots, they drag you down their level and beat you with experience. -
Sander deWaal
>Or the Russian 6C19 pi?
>http://home.planet.nl/~benadski/CO/6S19P.pdf
Hit "send" too fast.....
Here's more about the 6C19 pi:
http://www.jogis-roehrenbude.de/Russian/6C19N.htm
Ruud Broens
"Sander deWaal" <nos...@wanadoo.nl> wrote in message
news:19v602p1upnes3o26...@4ax.com...
: Sander deWaal <nos...@wanadoo.nl> said:
:
: >Or the Russian 6C19 pi?
: >http://home.planet.nl/~benadski/CO/6S19P.pdf
:
:
: Hit "send" too fast.....
: Here's more about the 6C19 pi:
: http://www.jogis-roehrenbude.de/Russian/6C19N.htm
:
: --
that's not small potatoes :-) buttah.. pp with 1 triode ??
turn up your crt dimmer, slick.
hehe,
Rudy
Sander deWaal
said:
>: Here's more about the 6C19 pi:
>: http://www.jogis-roehrenbude.de/Russian/6C19N.htm
>He Sander,
>that's not small potatoes :-) buttah.. pp with 1 triode ??
Never heard of single ended push pull, mmmmm?
;-)
>turn up your crt dimmer, slick.
>hehe,
>Rudy
Two of them, then?
John Stewart
You are absolutely correct. Not sure what I was thinking about.
Anyway, here is another tube to think about. I noticed AJ recommended a 6SN7. A 6BL7
has the same mu & can handle about double the power.
Now back to Aeroflex, IFR, Will'Tek & several others. More travellers coming to town
later this week. The world of hitech charges on!
Cheers, John
Iain Churches
This has turned into a very good thread:-)
I was planning a small SET amp next, but after reading
about potato amps, I am very interested to build one and
have a listen.
Could one of you collect some schematics, and give
this country boy some advice on a good tube with which
to start?
Regards to all,
Ruud Broens
: "Ruud Broens" , once again revealing his ignorance before us all,
: said:
:
:
: >: Here's more about the 6C19 pi:
: >: http://www.jogis-roehrenbude.de/Russian/6C19N.htm
:
:
: >He Sander,
: >that's not small potatoes :-) buttah.. pp with 1 triode ??
:
:
: Never heard of single ended push pull, mmmmm?
:
: ;-)
:
:
: >turn up your crt dimmer, slick.
: >hehe,
: >Rudy
:
:
: Two of them, then?
:
: --
needs the mother of all step-ups or _another tube_, eh ?
Rudy
Andre Jute
Rather than rewrite everything I've said in the past about potato amps,
I shall for a start merely reprint some earlier remarks under several
heads. First up is my original announcement of the reappearance of my
T17 "Solist" as the modified T68bis "Minus Zero", which is essentially
just the driving stage of my KISS 300B "Ultrafi".
Anyone who wants to follow this should bookmark this page
http://members.lycos.co.uk/fiultra/JUTE%20ON%20AMPS.htm
because much reference will be made to data and schematics referred to
at Jute on Amps; the connection is my high-sensitivity speakers which
fundamentally influences almost everything else I do. The T68bis "Minus
Zero" pics are available from Jute on Amps
http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
but John and Mick, who have hosted the Minus Zero and the HWAF horn
that goes with it since New Year's Day 2004 can find them directly on
their own sites. Thanks again, fellers.
Andre Jute
Visit Jute on Amps at http://members.lycos.co.uk/fiultra/
"wonderfully well written and reasoned information
for the tube audio constructor"
John Broskie TubeCAD & GlassWare
"an unbelievably comprehensive web site
containing vital gems of wisdom"
Stuart Perry Hi-Fi News & Record Review
Andre Jute
My original announcement of the T68bis "Minus Zero", unedited, so some
of the references may be obsolete. Pics at
http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
********
T68bis proves hedonists do more with less
rec.audio.tubes,aus.hi-fi
Gaincard, eat your heart out, Andre Jute is on the job
When I first read about the silicon Gaincard, I fell off my chair
laughing. This Japanese designer was earnestly putting forward a
philosophy of less is more. Thats what microwatt SE people have been
doing for years. He also sold his Gaincard bricks for a whole lotta
dollars, power supply extra.
The Gaincard was, if I remember correctly, 9 components per channel not
counting the stepped attenuator. That's the signal section only, not
including the power supply either.
The reason I fell of my chair laughing is that I already had two tube
amps, my T17 Solist and my T68 Minus Zero, with a lower parts count.
Now I am listening to a development of the T68, the T68bis. It has 3
components, a WE417A, a battery for bias, and a Lundahl LL1623 5K6
output transformer. Thats all. Grid leak is supplied by the DACT 100K
stepped attenuator. Output is 0.4W, which is more than enough to drive
the 100dB/W/m Lowther horns which I designed to go with the amp to
anti-social SPL. Though I am running the tubes at near enough 190V to
clear the grid current region which goes into the first 0.7V of
negative bias, dissipation at idle is only 2.85W.
The horns arent ready, or rather only one is ready, so Im playing the
Minus Zero bis through small Coral speaks built into coconuts by a
Swiss designer to use as upmarket multimedia speaks. They are high
quality but horribly inefficient little speakers. They sound very sweet
on four-tenths of a watt playing one of my killer test disks, Esther
Lamandier LEsprit de Dieu et les Prophetes, very clean considering that
Im using maximum output, the pot turned up almost all the way, just
enough left for a grid leak.
The power supply is responsible for the quality of the sound, of
course. Lundahl LL1651 power tranny, ballast resistors to stabilize the
AC, Mullard GZ34 with more ballasts in its filament supply, LL1638 dual
choke with special high common mode rejection termination scheme, Solen
56uF 400V, LL1638 connected across both B plus and earth lines, another
Solen cap, bleed resistor to burn off as more current than the tubes
will consume to further stabilize the supply. Star grounding for all
components to the low end of the bleed resistor.
This one may well turn out to be a keeper, though all that big Lundahl
iron of course gives the amp a Dunker Faktor of over 100, which is
excessive even for ultra-fi at this level. The Dunker Faktor is a
rating of how much an amp weighs per watt. Since lightweight amps
generally sound like shit, the higher the number the better the (tube)
amp is presumed to be. The T68 bis weighs 41lbs before casing (it is
tightly built on a 17 x 10 inch standard Hammond case bottom plate), so
the Dunker Faktor is 41 divided by 0.4 or 102.5. Thomas Dunker is a
Norwegian tube lover, amp builder and horn expert. If you're
interested in high efficiency speakers, visit his horn site.
Simplicity is very hard work. I first made the T17, of which the T68bis
is linear development, in 1994, ten years ago. But simplicity is almost
always the most rewarding concept sonically.
Tomorrow I shall organize a box for the amp, and get the horns up.
Andre Jute
Andre Jute wrote:
> My original announcement of the T68bis "Minus Zero", unedited, so some
> of the references may be obsolete. Pics at
> http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
> ********
>
> T68bis proves hedonists do more with less
etc -- see previous post in this thread. This conversation then ensued:
*******
Dissecting T68bis Minus Zero Re: Fulminations on vulgar display
rec.audio.tubes
I answer your points in position, John.
John Byrns <jby...@rcn.com> wrote:
>Andre Jute wrote:
> Fulminations on vulgar display
> rec.audio.tubes
>
> > Andre Jute wrote:
> > My present project, the T68bis Minus Zero has all the tubes
> > inside the box. Tubes on display are for newbies and ostentatious consumers.
> > Adult music lovers have no need of such vulgar display. . . .
>
> John Byrns <jby...@rcn.com> replied:
>
> As a compromise position it is hard to beat a pair of the original metal
> 6L6s, driven by 6SJ7 or similar tube of your choice. Exposed tubes
> without the ostentation.
> Regards,
> John Byrns
> Surf my web pages at, http://users.rcn.com/jbyrns/
>
> - - - - - -
>
> Heh-heh. You are wicked, John. Im sure you know I wrote that just to make the
> usual fulminators foam at the mouth, and that you saw the bit I wrote at the
> far, far bottom of that letter:
>
> . . . . Well, of course the real reason is that the two 417A, which are less
> than three-quarters of an inch long, look miserable on the aircraft carrier
> expanse of so much iron under the deck, and against even a small rectifier
> like the GZ34, indeed even against a nine-pin rectifier like the EZ81. Even
> if I boxed (on top of the chassis) the monstrous iron I use to guarantee an
> utterly silent amp, the tubes would look like little splotches of light
> against them, too bizarre for words. Even the rubber doughnuts I use to mount
> the chokes come halfway up the height of the 417A. . . .
>
> Andre Jute
>Hi Andre,
>What is the derivation of the "T68bis Minus Zero" nomenclature for this
amplifier?<
Type 68 is a design number in sequence, dating back to the mid-90s, bis
is the second development because the other related but much more
variant amps had separate numbers. Minus Zero because one of the others
was given the name Zero as it was under 1W and was designed for a
Japanese. Named amps avoid the confusion of type numbers, especially on
the phone in a mixture of languages.
>Is the bias battery in the cathode circuit of the 417A tube, or just in
the grid circuit?<
Cathode. The grid circuit is completed by the pot doubling as grid
leak, and, since I described the circuit a while back, four 220 ohm
grid stoppers to the four grid inputs.
>I think some work is needed on better industrial design for the amp than
your current "aircraft carrier" design.<
It is a novelty proto, most likely headed for the breakers to recover
the expensive components. I can't license the design because it would
compete with the one codenamed Zero, so I will play it until I build
something new and then it goes to a friend or the knackers.
>Since it sounds like each channel
draws only 15 mA from the supply<
Good God, no. Not worth building if you're trying to preserve 417A
for posterity. No, I'm running them at 190V, -2.4V bias and 27mA. The
417A is well known among the ultra-fi microwatters for being a very
hardy tube, well suited to running at 200V and 25mA. The 417A doesn't
come alive sonically until 20mA. Those who want to build a potato amp
of this quality without exceeding tube specs should instead look at the
even more expensive 437A or the cheap Russian 6P45S.
I'm also bleeding off another 20mA, for 74mA altogether.
>I would be tempted to ditch the GZ34,<
I had an EZ81 in there first. It didn't sound as good as the GZ34,
which I chose over my normal GZ37 simply because it fit inside the 4in
high standard Hammond ali case I wanted to use as a cover because I ran
out of time to make a custom cover.
> and make it a dual mono configuration using two EB91 7 pin rectifiers in a
full wave connection for each channel. The EB91s are about the same
size
as the 417A, the result would be six tubes of similar scale.<
You're assuming I actually want tubes on the outside. My iron is all
uncased, so it goes under the cover. The tubes would still look lonely.
> I would then
go for some smaller custom wound transformers, both outputs, and power,
designed specifically for this amplifier.<
I have smaller iron. I used the big iron for silence. That nonsense
that Creepy Mike used to put out about scaling power and output
transformers just right was commercial waffle from a time when he made
only smallish stuff. My experience is that oversizing your iron pays
off big in everything except bills.
>I would try to scale the
chassis down from the current "aircraft carrier" size to as compact a
size
as I could make it.<
It is now 17in x 10 x 4, and the footprint, since it stands on its end,
is 10 x 4in, not excessive, even visually next to a stack of CD players
and preamps with a printer on top. (I've taken Mick up on his offer
to publish a photograph on his site, and sent him a PDF of the amp and
accompanying horns to his mailbox. I haven't seen him around since
though. If he publishes it, you'll be able to see the scale.) My
aircraft carrier reference was to the bare deck, with only connectors
on it.
> I would mount the transformers to the bottom plate of
the chassis, and have them protrude through holes in the top of the
chassis, with the portion of the transformers above the chassis covered
by
enclosures of a scale appropriate to the tubes.<
Hmm. I actually have suitable casework for that already, a
pre-production sample sent for my approval on another design. It even
has suitable transformers bolted in already.
> Then maybe round off the
corners of the chassis, and chrome the whole works to make the most of
the
small tubes.<
I don't use chrome, except for some chrome knobs a manufacturer sent
me for a design because they have such wonderful heft. I like plain
metals. But the casework described above is even better than chrome,
polished stainless steel.
Generally speaking, I am less than overwhelmed by tiny-case tube amps.
There is always a heat problem. I even took an opamp gaincard type I
built out of a 4 x 4 x 2 box and put it in one 6 x 4 to help it run
cooler. Very often in my amps, I need the expanse of ali or copper as a
heatsink for big power resistors in the ballasts and the bleed and the
voltage dropper for the rectifier.
>What iron does the "T68bis Minus Zero" use besides the input, output, and
power transformers? How many chokes in the power supply?<
Ah. It was originally intended to use input transformers, but I wrecked
the terminal on one of the pair and my spare pair is out on loan to
someone. It uses an LCLC supply, with two big Lundahl LL1638 10H
double-chokes. One is connected in series across the main line, and one
is split across the top and return lines for improved common mode
rejection. The two caps in the power filter are also the only caps in
the entire amp. They are both polyprops, of course. They add up to
112uF. A Stateside chum has written to tell me that Lucas Cant, the
best Australian transformer winder, who among other ultra-fi
transformers offers iron specifically designed for 417A potato amps,
advises bumping the 100uF of capacitance widely used to 200uF if the
amp is noisy, but mine is dead quiet. Lucas, IIRC, sells a 6K primary
OPT for this purpose, near enough the 5K6 I chose, so he too trades
power for silence. Of course, being a manufacturer, he probably also
advises running the tubes much cooler than I do on my wildcard
temporary Christmas proto, probably well within book spec. I'm too
sleepy now to check whether Lucas is on the net or whether I got the
details of his transformer I remember from someone at the Joenet, maybe
a Melbourne maker of class A solid state kit amps called Hugh Deane
>Oh, and I would try to lose that battery too.<
You're having me on, John. That battery knocks out the most
significant deleterious soundshaping component in the whole amp, the
cathode bypass cap. It's the battery that is responsible for this
little amp's truly superior sound, even at full power. If you're
planning on building a similar amp with an RC cathode circuit rather
than a battery, don't bother. I just don't see the point of
building an entire amp for silence and sonic purity and then wrecking
all the hard development work with that cap in the cathode.
>Regards,
>John Byrns
>Surf my web pages at, http://users.rcn.com/jbyrns/
Of course, before you can even consider building an amp like this (or a
much cheaper version with multiple el cheapo 7044 I knocked up a few
years ago), you need high-sensitivity speakers. They don't need to be
Lowthers or even corner horns. I have a pair of 2 or 2.5 in Corals
stuck into coconuts as a novelty by a Swiss designer on my desk, and
they work superbly with this amp. In fact I am wondering where I can
get more, to make little speakers for my son, because I don't want to
let these go. If you have space for a big footprint speaker, my
Impresario and Thorsten's Afterburner which both use an inexpensive
Eminence guitar driver, and the much more expensive but probably better
Hammer version of the same driver in a similar box, are all sensitive
enough to use with an amp with 400mW output.
In fact, the tubes I already mentioned aren't the only options. As we
discussed a few years ago, you can make a small power amp with 6SN7,
and an EL84 in pseudo-triode mode SE sounds superb too. There's a
good little commercial kit amp, called Dec IIRC, which goes the EL84
route and claims something like 4 or 5W, which I can't say I've
seen with trioded EL84 but still much, much more power than 417A. The
417A and the 437A are used by the ultra-fidelista microwatters despite
their outrageous price from WE because they truly have superior sound.
Andre Jute
The true math of hi-fi is subtraction
Andre Jute
Andre Jute wrote:
> My original announcement of the T68bis "Minus Zero", unedited, so some
> of the references may be obsolete. Pics at
> http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
> ********
> T68bis proves hedonists do more with less
> rec.audio.tubes,aus.hi-fi
etc snipped.
Below is part of correspondence with John Byrns about the dissipation
of the 417A in my potato amp and, much more important (at least if you
have plenty of 417A!) the placement of the battery bias in various
positions in the input circuit.
******
Re: Dissecting T68bis Minus Zero
rec.audio.tubes
John:
If I said the anode dissipation was 2.85W, that was probably in a
planning stage, a mistake or possibly wishful thinking. The exact
numbers in the amp when I measured it quickly for a safety check on
getting it up, was bias -2.88V, plate 189V, so the current, from the
IaEgEb curves, comes to something over 25mA. I'm enjoying playing it
too much to put it back on the bench for measurements. Anything over
20mA will do me. I would know from the limp sound if the tubes drew
less.
Very generous of you to offer me space to put up a few photographs of
this amp and its associated twin-channel horn. Last night I sent you a
zipped PDF file as an attachment to private mail. If you didn't get
it, let me know and I will try again.
I have saved your paragraph on impedance in the cathode circuit. I
shall hold my fire on the battery as a soundshaping component until
your >monograph explaining the problem with placing any component in
the cathode circuit, and why any component in the cathode circuit acts
as a soundshaping circuit, even a battery< appears, because at that
point I may want to pretend I knew all that all along. Meanwhile I will
say that I have tried batteries both in the cathode circuit and in the
grid circuit (convenient if there is a pot associated with the battery
to fine tune the bias) but cannot now remember an occasion where I
tried both in the same amp, so I cannot say yeah or nay. I have a bunch
of nicads sitting on my desk because the wireless mouse for my new Mac
chews them, and I am now regarding them with grim suspicion. . . (1)
Andre Jute
Capacitor exterminator
(1) If you aren't paranoid, what are you doing in high voltage
electrics?
John Byrns <jby...@rcn.com>
In article <BW644VK537985.5839930556@anonymous>, Anonymous
<Bigapple...@Optonline.Net> wrote:
> John Byrns <jby...@rcn.com> wrote:
> >Andre Jute wrote:
>
> >Since it sounds like each channel
> > draws only 15 mA from the supply<
>
> Good God, no. Not worth building if youre trying to preserve 417A for
> posterity. No, Im running them at 190V, -2.4V bias and 27mA. The 417A is well
> known among the ultra-fi microwatters for being a very hardy tube, well suited
> to running at 200V and 25mA. The 417A doesnt come alive sonically until 20mA.
> Those who want to build a potato amp of this quality without exceeding tube
> specs should instead look at the even more expensive 437A or the cheap Russian
> 6P45S.
I thought you said in an earlier post that you were running the 417A's
at
about 190 volts, and the anode dissipation was 2.85 Watts, or was that
an
earlier variant of the amp?
> It is now 17in x 10 x 4, and the footprint, since it stands on its end, is
> 10 x 4in, not excessive, even visually next to a stack of CD players and
> preamps with a printer on top. (Ive taken Mick up on his offer to publish a
> photograph on his site, and sent him a PDF of the amp and accompanying horns
> to his mailbox. I havent seen him around since though. If he publishes it,
> youll be able to see the scale.) My aircraft carrier reference was to the bare
> deck, with only connectors on it.
If Mick doesn't publish it, I would be happy to publish it for you on
my
web pages.
> >Oh, and I would try to lose that battery too.<
>
> Youre having me on, John. That battery knocks out the most significant
> deleterious soundshaping component in the whole amp, the cathode bypass cap.
> Its the battery that is responsible for this little amps truly superior sound,
> even at full power. If youre planning on building a similar amp with an RC
> cathode circuit rather than a battery, dont bother. I just dont see the point
> of building an entire amp for silence and sonic purity and then wrecking all
> the hard development work with that cap in the cathode.
No, you are of course correct that the cathode bypass capacitor is a
soundshaping component, but I find batteries in the cathode circuit to
be
even more egregious soundshaping components when used in the cathode
circuit, although many audiophiles today seem to like the euphonic
sound
of a battery in the cathode circuit.
The truth of the matter is that the only way to achieve a truly neutral
sound with a minimum of soundshaping is to eliminate any impedance in
the
cathode circuit, which is common to both the grid and anode circuits
forming a soundshaping feedback circuit, and connect the cathode
directly
to the negative supply rail eliminating the common impedance from the
plate and grid circuits. This necessitates injecting the bias into the
grid circuit only, and for this purpose you can use a battery, a
separate
power supply, or a back bias scheme. In the case of the T68bis Minus
Zero
I would suggest putting the 2.4 volt battery directly in the grid
circuit
between the input pot and grid stoppers, as that would be most in
keeping
with the spirit of the amplifier, while eliminating the soundshaping
components from the cathode circuit.
I can see that I am going to have to publish a monograph explaining the
problem with placing any component in the cathode circuit, and why any
component in the cathode circuit acts as a soundshaping circuit, even a
battery.
Andre Jute
Andre Jute wrote:
> Iain Churches wrote:
> > Greetings, John, Andre et al.
> >
> > This has turned into a very good thread:-)
> >
> > I was planning a small SET amp next, but after reading
> > about potato amps, I am very interested to build one and
> > have a listen.
There is a serious problem with building potato amps that John has
already run into: potato tubes don't fall off trees. The 417A I use is
good for much less than a watt even when hogged out and, applied with
my usual conservatism and powerhogging devices to shape the residual
distortion spectrum favourably, in fact for only a third of a watt. The
implication is that your speakers had better be 100db/m inbox, which my
Lowther Fidelio fortunately are. My Impresario is an inexpensive
speaker which works with very low power amps:
http://members.lycos.co.uk/fiultra/KISS%20195%20The%20Impresario.jpg
but there was recently a thread here on RAT in which a fellow called
Tom from Germany (possibly Belgium?) showed us some fabulous small
horns with inexpensive drivers that would very likely be superior if
the woodwork does not frighten one.
The 417A is a standin tube. Traditionally the ultrafidelista built
their potato amps with 437A, the 417A's big brother, and got a very
clean watt and a half. The 437A is now rare and expensive. The STC 167M
is a direct sub.
The Russian 6C45P or (pi and other variants of the cyrillic spelling)
looks like a good substitute for the 437A. There have been matching
problems with this Russian tube and I have never had a good pair but
others have been more fortunate.
The 6DN7 as used by Dan Schmalle for his SEX amp is good for 2W. I
built the SEX for my review in Glass Audio and found it a good amp,
bigger-sounding than its antecendents and price would indicate. I would
say, actually, that the SEX is at the top end of the price range for a
potato amp. The SEX is a well-developed circuit. The layout is
important, which is why for my T68 I published the layout rather than
the circuit.
I'm not just being controversial for the sake of it. I think John has
the right power range: 1W is good for general use among good sensitive
speakers and 2W is already verging towards excess with the most
sensitive speakers but always useful for grabbing control of the
speaker in larger-scale music. It is perfectly all right for people
like us, who have several other amps, to build a potato amp as a
novelty, but we shouldn't encourage anyone to build the smallest potato
amps as their first amps. My socalled "potato amp" is in fact a testbed
for a 300B amp driver stage and I have since put the 300B back on it.
As such my potato amp is the total cost of a 300B amp less only the
1300 Euro or so a pair of matched WE300B costs after carriage and
taxes. But any good potato amp will not be cheap: when there are so few
components, those that are there must be of the very best quality
because you can, quite literally, hear every single component. It would
be easier, for instance, to get away with less than the best iron on a
PP amp than on a potato amp.
Again, I'm not just tweaking the noses of the unholy because they have
no business sticking them into my hobby, I'm in dead earnest. Replace
the battery bias of my T68 with a cap and the effect is instantly
audible. Now swap between electrolytic and polyprop caps in the cathode
and you can hear the difference. Change the cap type or rating in the
power filter and, bingo, you can hear what electrolytics sound like and
what polyprops or oil caps sound like. Even the position of the battery
for bias makes a difference, just as John says.
So, unless you chose wisely, the huge simplicity of the potato amp can
be an illusory advantage, and the cost advantage is either nil or
negative. A "simple" potato amp, paraxodically, is a privileged tubie's
indulgence.
It is in fact easier and cheaper to build a three tube SE amp, as in my
T201 SEntry, which uses one 6SN7 to drive two trioded EL34 to a
glorious total of 2W. Schematic here:
http://members.lycos.co.uk/fiultra/Jute-EL34-SEntry.jpg
This was designed to be built cheaply, with a common widely catalogued
iso transformer for mains and a couple of filament transformers, plus
small 3K outputs which are cheap enough. I made the one for my son's
mantelpiece at college with two small spare upright transformers facing
each other for isolation. Yet the sound is fantastic, quite out of
proportion to the cost. For those who do not have sensitive speakers,
my T201 is definitely a better option, not least for its much greater
versatility.
> > Could one of you collect some schematics, and give
> > this country boy some advice on a good tube with which
> > to start?
One doesn't draw out a schematic for a potato amp, one calculates it on
the fly! Actually, I see I have a circuit standing on my computer for
my original T17 "Solist" of the period 1992-1994, reverse-engineered
after the event when I licensed the design, so I'll adapt that to the
T68 and post it to my netsite for you. All potato amps follow the same
pattern.
> > Regards to all,
> >
> > --
> > Iain
> > www.kolumbus.fi/iain.churches
HTH.
John Byrns
<taelN...@kolumbus.fi> wrote:
> Greetings, John, Andre et al.
>
> This has turned into a very good thread:-)
>
> I was planning a small SET amp next, but after reading
> about potato amps, I am very interested to build one and
> have a listen.
>
> Could one of you collect some schematics, and give
> this country boy some advice on a good tube with which
> to start?
Hi Iain,
There are at least three types of "potato" amp that I can think of. First
is the single triode amplifier like Andre's Type 68bis 417A amplifier
which inspired me to think about a push pull version. I assume Andre
could provide a schematic and parts list for the construction of his Type
68bis amplifier.
The second and much more common form of "potato" amp are the many SE
designs based on asymmetrical dual triode tubes. Andre has pointed out
that the so called "SEX" amplifier is of this type, there are many more
examples on the web.
Finally there is the push pull "potato" amplifier like I am looking at
building. I have not seen any examples of this type before. I am looking
at using the 7044 dual triode that Andre mentioned in another thread.
Using the class A design parameters posted last week by Patrick turner, I
figure I can get about 1.8 Watts out of a 7044 in push pull with an anode
voltage of 165 volts, a quiescent current of 19.4 mA per triode section,
and a load of 10k anode to anode.
Which sort of "potato" amplifier are you interested in? The Single Ended
asymmetrical triode designs are probably the most practical as there is
plenty of gain to be easily had, providing plenty of input sensitivity.
There are also dozens of different tubes to choose from, one for just
about any taste.
Andre Jute
qualifies as a "potato amp". Clearly any amp with a single tube for
both channels and all stages is a "potato amp" par excellence. Such a
thing is possible. I was told one day in conversation with the then
owner of Arion that they had such a single tube amp on the bench and
intended marketing it. I heard nothing after that and can't find any
reference on the net (make yourself useful, Ross Matheson!).
Okay, potato amps are
1. A single tube per channel. My T68 "Minus Zero" is without a doubt a
potato amp. It has one 417A per channel and is driven directly from the
source, a CD, and outputs through output transformers into the
speakers.
2. A single glass envelope for all channels and all functions, as in
the Arion described above. I don't know what the input requirement was.
3. A single glass envelope per channel containing driver and power
tubes, as in the SEX.
4. A single tube or envelope per channel, with iron stepping up the
signal from the source, as in John's example already in this thread.
A tube rectifier does not count in the complement of tubes.
We appear to be assuming that a potato amp is one that takes the signal
from the source without benefit of a pre-amp to provide gain. But if a
step-up insterstage is permissable, why not a pre-amp with gain?
It seems to me that the guys who first built potato amps had nothing
but vinyl, and that most of those who now build potato amps (the ones I
know anyway, excluding only me) are vinyl freaks. A phono pre-amplifier
is therefore almost a given, rather than the CD player I use. To them a
potato amp was and is a *power* amp with only one tube.
I'll answer my own question. I think that, all the same, under modern
conditions we want to define a potato amp as one which takes a CD
signal or a phono-amplified signal of say 2V, and uses only a single
envelope per channel, not counting rectifiers. Iron, as in interstages,
is a free option (my T68 was originally intended to have input
transformers so it could be put behind the speakers with the pot pot
nearer to my hand). Obviously no active devices (transistors, ugh!) are
allowed because that would not be a potato amp but a hybrid amp.
Offered for discussion.
Andre Jute
John Byrns wrote:
> Hi Andre,
>
> Please forgive me if I have asked this question before, but how did your
> Potato Amp come by its name?
>
>
John Stewart
> John Byrns wrote:
> > Hi Andre,
> >
> > Please forgive me if I have asked this question before, but how did your
> > Potato Amp come by its name?
>
> Potato Amp is not the amp's name; it merely describes a single-tube
> amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
> I don't know who first made the pun. I heard it first from Dan
> Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
> Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
> consideration whether an amp built with two tubes in one envelope (per
> channel) is still a potato amp. An example would be Dan's Single-Ended
> Experimenter's or SEX; I had a sidebar in my original review for Glass
> Audio of the SEX amp on the lexicography of potato amps but the editor
> preferred to give the sidebar space to an advertisement...
Which issue of GA contains that article? I have them all here. I would like to
have a look, not at the ad but rather the potato!
My 'Potato Amp' if that is what they are called was published in GA Issue 4,
2000 with photos, schematics & comprehensive test results. The test results
were taken both with & without NFB.
At the time I didn't know it would become a potato. It uses a 6EA7/6EM7
dissimilar triode, driving into a Hammond 125E Universal OPT. It would do a
lot better at the low frequencies with one of the newer Hammond OPT designed
specifically for SE circuits. It also includes a line stage & Baxandall Tone
circuit.
A more powerful version using a 6LU8 connected either triode or UL appears in
the Glass Audio Projects book. See the GA Projects book at
http://www.audioxpress.com/bksprods/books/bkaa62.htm
Cheers, John Stewart
> > Regards,
> >
> > John Byrns
> >
> > Surf my web pages at, http://users.rcn.com/jbyrns/
>
Andre Jute
John Stewart wrote:
> Andre Jute wrote:
>
> > John Byrns wrote:
> > > Hi Andre,
> > >
> > > Please forgive me if I have asked this question before, but how did your
> > > Potato Amp come by its name?
> >
> > Potato Amp is not the amp's name; it merely describes a single-tube
> > amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
> > I don't know who first made the pun. I heard it first from Dan
> > Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
> > Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
> > consideration whether an amp built with two tubes in one envelope (per
> > channel) is still a potato amp. An example would be Dan's Single-Ended
> > Experimenter's or SEX; I had a sidebar in my original review for Glass
> > Audio of the SEX amp on the lexicography of potato amps but the editor
> > preferred to give the sidebar space to an advertisement...
>
> Which issue of GA contains that article? I have them all here. I would like to
> have a look, not at the ad but rather the potato!
Volume 9, no 6, 1997, p54ff.
It is years since I gave away the SEX. I now see that it is a PSE amp,
not an SE amp at all -- cf circuit p61. It therefore doesn't qualify as
a potato amp. Embarrassing that, as I am talking to John Stewart, who
remembers what he built forty and fifty years ago from a circuit
published in 194x... Sorry, folks.
> My 'Potato Amp' if that is what they are called was published in GA Issue 4,
> 2000 with photos, schematics & comprehensive test results. The test results
> were taken both with & without NFB.
>
> At the time I didn't know it would become a potato.
If it's one envelope per channel, it's a potato amp. I made an analysis
in a different thread of what is and isn't a potato amp and offered it
for discussion but John Byrns has made a much more concise and pointed
analysis in this thread and I think we should accept that.
>It uses a 6EA7/6EM7
> dissimilar triode,
That meets one of John's, and my, definitions.
Andre Jute
Andre Jute
John Byrns wrote:
> In article <du1jhj$dir$1...@phys-news4.kolumbus.fi>, "Iain Churches"
> <taelN...@kolumbus.fi> wrote:
>
> > Greetings, John, Andre et al.
> >
> > This has turned into a very good thread:-)
> >
> > I was planning a small SET amp next, but after reading
> > about potato amps, I am very interested to build one and
> > have a listen.
> >
> > Could one of you collect some schematics, and give
> > this country boy some advice on a good tube with which
> > to start?
>
> Hi Iain,
>
> There are at least three types of "potato" amp that I can think of.
First off, I think this is the perfect analysis. It includes everything
we need to define a potato amp: one envelope per channel.
> First
> is the single triode amplifier like Andre's Type 68bis 417A amplifier
> which inspired me to think about a push pull version. I assume Andre
> could provide a schematic and parts list for the construction of his Type
> 68bis amplifier.
>
> The second and much more common form of "potato" amp are the many SE
> designs based on asymmetrical dual triode tubes. Andre has pointed out
> that the so called "SEX" amplifier is of this type, there are many more
> examples on the web.
I gave those SEX away almost as soon as I finished testing them. I have
since (meaning just now) checked the schematic in Glass Audio Volume 9
No 6 1997 p61 and discovered what I had forgotten, that the SEX isn't a
potato amp. It is a PSE amp... John Stewart points to two other amps
from GA which are potato amps, though he didn't know the terminology
(you want to mix with a better class of audiophile, John!).
************
John Stewart wrote:
> My 'Potato Amp' if that is what they are called was published in GA Issue 4,
> 2000 with photos, schematics & comprehensive test results. The test results
> were taken both with & without NFB.
>
> At the time I didn't know it would become a potato. It uses a 6EA7/6EM7
> dissimilar triode, driving into a Hammond 125E Universal OPT. It would do a
> lot better at the low frequencies with one of the newer Hammond OPT designed
> specifically for SE circuits. It also includes a line stage & Baxandall Tone
> circuit.
>
> A more powerful version using a 6LU8 connected either triode or UL appears in
> the Glass Audio Projects book. See the GA Projects book at
>
> http://www.audioxpress.com/bksprods/books/bkaa62.htm
***********
Here we return to John Byrns's post:
> Finally there is the push pull "potato" amplifier like I am looking at
> building. I have not seen any examples of this type before. I am looking
> at using the 7044 dual triode that Andre mentioned in another thread.
> Using the class A design parameters posted last week by Patrick turner, I
> figure I can get about 1.8 Watts out of a 7044 in push pull with an anode
> voltage of 165 volts, a quiescent current of 19.4 mA per triode section,
> and a load of 10k anode to anode.
Clearly, a PP potato is higher level of challenge than the single
triode or dissimilar triode SE amp model. The 7044 is a tube with
everything except reputation. If the name on the glass were Western
Electric, it would be famous and overpriced. I missed the specs given
by Patrick. This sounds like you don't have curves. The 7044 is a tube
for which it is ferociously difficult to get reliable and usable
information. But I now have a PDF (216KB) I can forward to you on
request, and I have taken out the curves and enlarged them to make them
more usable (416KB). I also have various published tables (2.6MB) I can
send if required. Just ask; no problem as I have broadband but I don't
just want to send stuff if it will clog up your coms forever.
> Which sort of "potato" amplifier are you interested in? The Single Ended
> asymmetrical triode designs are probably the most practical as there is
> plenty of gain to be easily had, providing plenty of input sensitivity.
> There are also dozens of different tubes to choose from, one for just
> about any taste.
These have been mentioned:
6DN7
6EA7/6EM7
6LU8
> Regards,
> John Byrns
> Surf my web pages at, http://users.rcn.com/jbyrns/
Andre Jute
phatty mo
> My original announcement of the T68bis "Minus Zero", unedited, so some
> of the references may be obsolete. Pics at
> http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
> ********
>
> T68bis proves hedonists do more with less
> rec.audio.tubes,aus.hi-fi
>
>
> Gaincard, eat your heart out, Andre Jute is on the job
>
> When I first read about the silicon Gaincard, I fell off my chair
> laughing.
Yea,me too.Have you seen the pics of the insides of one?
"Hand wired" by someone who didn't know how to solder,by the looks of
it.The insulation on the ends of the wires is all melted and burned,and
stripped back much too far,possible short-circuit hazard.Quite messy.
The "special" components looked like old carbon comp resisors,and some
'generic' caps from the junkbox..
I was not impressed,no matter how it sounds,for that price.
I made a "gainclone" type setup with a TDA chip of some sort(forget
which one now) Nothing fancy,it sounded good though,and used hardly any
components -The IC,3 caps,and the input pot! A nice 20Wpc.
It took me like 30 minutes to wire up the stereo amp from junkbox parts..
I wonder if I could sell it for $5K.. ;-)
Andre Jute
phatty mo wrote:
> Andre Jute wrote:
> > My original announcement of the T68bis "Minus Zero", unedited, so some
> > of the references may be obsolete. Pics at
> > http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
> > ********
> >
> > T68bis proves hedonists do more with less
> > rec.audio.tubes,aus.hi-fi
> >
> >
> > Gaincard, eat your heart out, Andre Jute is on the job
> >
> > When I first read about the silicon Gaincard, I fell off my chair
> > laughing.
>
>
> Yea,me too.Have you seen the pics of the insides of one?
> "Hand wired" by someone who didn't know how to solder,by the looks of
> it.The insulation on the ends of the wires is all melted and burned,and
> stripped back much too far,possible short-circuit hazard.Quite messy.
> The "special" components looked like old carbon comp resisors,and some
> 'generic' caps from the junkbox..
> I was not impressed,no matter how it sounds,for that price.
I used to work in advertising. I had wallpaper printed and put up in
all our offices with on it the text, "The consumer isn't a moron, she's
your wife. -- David Ogilvie".
> I made a "gainclone" type setup with a TDA chip of some sort(forget
> which one now) Nothing fancy,it sounded good though,and used hardly any
> components -The IC,3 caps,and the input pot! A nice 20Wpc.
> It took me like 30 minutes to wire up the stereo amp from junkbox parts..
> I wonder if I could sell it for $5K.. ;-)
Pretend to be Japanese. Speak slowly and distincly. Say, "The sound of
the stones is the infinity of silence between the grains of my wisdom."
Refuse to answer questions; just repeat your mantra in different ways.
Soon people will think 5K is too little to pay for the privilege of
associating with your wu. Send me a commission.
My own gainbrick is here:
http://members.lycos.co.uk/fiultra/KISS%20191A%20by%20Andre%20Jute.htm
http://members.lycos.co.uk/fiultra/KISS%20191B%20by%20Andre%20Jute.htm
http://members.lycos.co.uk/fiultra/KISS%20191C%20mGBschem.jpg
http://members.lycos.co.uk/fiultra/KISS%20191D%20mGBmatr.jpg
http://members.lycos.co.uk/fiultra/KISS191E%20NoBleed.jpg
HTH.
Andre Jute
Andre Jute
flipper wrote:
> On 28 Feb 2006 17:08:24 -0800, "Andre Jute" <fiu...@yahoo.com> wrote:
> >I think that, all the same, under modern
> >conditions we want to define a potato amp as one which takes a CD
> >signal or a phono-amplified signal of say 2V, and uses only a single
> >envelope per channel, not counting rectifiers. Iron, as in interstages,
> >is a free option (my T68 was originally intended to have input
> >transformers so it could be put behind the speakers with the pot pot
> >nearer to my hand). Obviously no active devices (transistors, ugh!) are
> >allowed because that would not be a potato amp but a hybrid amp.
>
> 316mVrms (I've also seen amps spec'ing 707-775mVrms) and Pro is about
> 1.228Vrms so where does the 2V (rms?) come from?
Yeah, right, I have a Velleman K4000 triple EL34 PPP I built from a kit
that has 775mV rms as an input level. Someone once told us what it
related to, but I can't find it now.
2Vrms is what my Quad 66 and 67 CDs put out. I've been told several
times that most CD players put out 2Vrms.
Andre Jute
Andre Jute
flipper wrote:
> On 28 Feb 2006 15:37:08 -0800, "Andre Jute" <fiu...@yahoo.com> wrote:
>
> >
> >My original announcement of the T68bis "Minus Zero", unedited, so some
> >of the references may be obsolete. Pics at
> >http://members.lycos.co.uk/fiultra/KISS%20192%20T68MZ417A.jpg
> >********
> >
> >T68bis proves hedonists do more with less
> >rec.audio.tubes,aus.hi-fi
> >
> >
> >Gaincard, eat your heart out, Andre Jute is on the job
> >
> >When I first read about the silicon Gaincard, I fell off my chair
> >laughing. This Japanese designer was earnestly putting forward a
> >philosophy of less is more. Thats what microwatt SE people have been
> >doing for years.
>
> 'microwatts'. The 'less' they mean is parts count and wire lengths. (I
> realize you go on to talk about parts count. Just clarifying that
> 'less power' ain't in the equation).
>
> > He also sold his Gaincard bricks for a whole lotta
> >dollars, power supply extra.
> >
> >The Gaincard was, if I remember correctly, 9 components per channel not
> >counting the stepped attenuator. That's the signal section only, not
> >including the power supply either.
>
> bit misleading as they count the entire amplifier, ostensibly an
> LM3875/LM3886 I.C. according to the gaincloners, as 'one part' but
> that 'one part' contains (according to the equivalent circuit for the
> LM3886) some 19 transistors, not counting the some 7 active current
> sources, plus over 25 various diodes and resistors that belie their
> 'motto' of "Only the simplest can accommodate the most complex"
> (further clarified by their "Extreme simplicity ----- minimum
> circuitry" 'feature' claim) as an amplifier with that many devices is
> anything but 'simple' regardless of being encased as 'one part'.
> Might be 'simple' to assemble since the I.C. manufacturer has done all
> the complex work but that isn't the gist of their claim. When did the
> internals of an Integrated Circuit cease being a "circuit'?
>
> To be fair, the amp being an I.C. could be considered consistent with
> their 'short wire' path argument although they don't seem to dwell on
> it being an I.C. as part of the 'secret'.
You could also say that in tubes the DHT has "invisible parts" in the
vacuum and its arrangement which causes negative feedback, possibly
12dB in a 300B. That is, the directly heated triode is itself a sort of
gainblock.
> But using the 'part' argument one could claim an Athlon64, with it's
> some 105.9 MILLION transistors, is 'simple' because they're all in one
> I.C. package and I seriously doubt anyone is going to fall for that
> one.
>
> If you want to beat a gaincard in the 'parts count' game just build a
> gainclone and pot the whole thing into a brick. There ya go, it's all
> 'one part' now. Beat that.
Yeah. I had more to say about gaincards and gainbricks a year or so
later when I built one as an alternative to Pinkerton's KISASS travesty
when it became clear KISASS would, if anyone ever decided to build
something so incompetent, sound nothing like a tube amp.
My own gainbrick is here:
http://members.lycos.co.uk/fiultra/KISS%20191A%20by%20Andre%20Jute.htm
http://members.lycos.co.uk/fiultra/KISS%20191B%20by%20Andre%20Jute.htm
http://members.lycos.co.uk/fiultra/KISS%20191C%20mGBschem.jpg
http://members.lycos.co.uk/fiultra/KISS%20191D%20mGBmatr.jpg
http://members.lycos.co.uk/fiultra/KISS191E%20NoBleed.jpg
Andre Jute
John Stewart
Cheers, John Stewart
TABLE ONE
SUMMARY OF POWER TRIODES ACCOMPANIED BY
A VOLTAGE AMPLIFIER
TYPE mu T1
mu T2 T2 WATTS BASE
CONNEXION
6BL7GTA 15
15 10
OCT 8BD
6BX7
10 10 10
OCT 8BD
6CY7
68 5
5.5 MIN
9LG
6DE7,10,13 17.5 6
7 MIN
9HF
6DN7
22.5 15.4 10
OCT 8BD
6DR7,10,13 68
6 7
MIN 9HF
6EA7
66 5.5 10
OCT 8BD
6EM7,10,13 64
5.4 10
OCT 8BD
6EW7
17.5 6 10
MIN 9HF
6FD7, 13 64
6 10
MIN 9HF
6FJ7
22.5 15.4 10
COMP 12BM
6FM7,13,15 66 5.5
10 COMP
12EJ
6FR7
68 5.4 10
MIN 9HF
6FY7, 15 65
6 7
COMP 12EO
6GF7,10,13 64 5.4
11 NOVAR
9QD
6GL7
66 5
10 OCT
8BD
Stewart Pinkerton
>I see.
>
>The specs I found for a Quad 66 (on Ebay) said "2 V rms max. 300 mV on
>normal programme material." Is that due to a volume control or a
>nominal 316mV with 16dB headroom?
2V rms at 0dBFS is the international standard for CD players, but
several 'high end' players and DACs put out considerably more for some
reason. The lower voltage on the Quad spec will relate to the average
output level of a (probably classical) music CD.
--
Stewart Pinkerton | Music is Art - Audio is Engineering
Ian Iveson
>>flipper wrote:
>>>> I'm curious about the 2V number. 'Consumer' line level is about
>>>> 316mVrms (I've also seen amps spec'ing 707-775mVrms) and Pro is about
>>>> 1.228Vrms so where does the 2V (rms?) come from?
>>>
>>>Yeah, right, I have a Velleman K4000 triple EL34 PPP I built from a kit
>>>that has 775mV rms as an input level. Someone once told us what it
>>>related to, but I can't find it now.
>>>
>>>2Vrms is what my Quad 66 and 67 CDs put out. I've been told several
>>>times that most CD players put out 2Vrms.
>>>
>>>Andre Jute
>>
>>I see.
>>
>>The specs I found for a Quad 66 (on Ebay) said "2 V rms max. 300 mV on
>>normal programme material." Is that due to a volume control or a
>>nominal 316mV with 16dB headroom?
>
> 2V rms at 0dBFS is the international standard for CD players, but
> several 'high end' players and DACs put out considerably more for some
> reason. The lower voltage on the Quad spec will relate to the average
> output level of a (probably classical) music CD.
> --
They'd be lost without you, Stewart.
cheers, Ian
Iain Churches
"Stewart Pinkerton" <pat...@dircon.co.uk> wrote in message
news:q2nb021b0jiedgfsk...@4ax.com...
That seems about right. I have just looked at the
average level of a Decca recording of Anton Bruckner
Symphony no.4 in Eb major. It spends a lot of time at and below
-15 dBFS.
Iain
John Byrns
Jute" <fiu...@yahoo.com> wrote:
> Clearly, a PP potato is higher level of challenge than the single
> triode or dissimilar triode SE amp model. The 7044 is a tube with
> everything except reputation. If the name on the glass were Western
> Electric, it would be famous and overpriced. I missed the specs given
> by Patrick. This sounds like you don't have curves. The 7044 is a tube
> for which it is ferociously difficult to get reliable and usable
> information. But I now have a PDF (216KB) I can forward to you on
> request, and I have taken out the curves and enlarged them to make them
> more usable (416KB). I also have various published tables (2.6MB) I can
> send if required. Just ask; no problem as I have broadband but I don't
> just want to send stuff if it will clog up your coms forever.
Hi Andre,
Thanks for the offer of the 7044 data sheet, but I have already downloaded
one and so don't require another copy. The 7044 has lead me to another
tube, the E182CC which appears to be even more suited to my needs, as the
transconductance is 15,000 umohs while the trnsconductance of the 7044 is
only 12,000 umhos. I am on the lookout to purchase some on eBay for my pp
"potato" project.
For the time being I have decided to go with a high impedance center taped
choke for the phase inverter rather than a transformer as I don't have a
suitable transformer in my junk box. I will keep my eyes open on eBay
although the type of transformer I want is rare as hen's teeth and the
best substitute goes for big money. Without the 1.5 step-up ratio in a
transformer I will be down about 3 dB on sensitivity relative to your 417A
"potato" amp.
You didn't miss the class A design "specs." given by Patrick, he posted
his piece on the 22nd IIRC, and you posted a message in response to his,
so you should remember it.
John Byrns
Jute" <fiu...@yahoo.com> wrote:
> flipper wrote:
> > On 28 Feb 2006 17:08:24 -0800, "Andre Jute" <fiu...@yahoo.com> wrote:
> > >I think that, all the same, under modern
> > >conditions we want to define a potato amp as one which takes a CD
> > >signal or a phono-amplified signal of say 2V, and uses only a single
> > >envelope per channel, not counting rectifiers. Iron, as in interstages,
> > >is a free option (my T68 was originally intended to have input
> > >transformers so it could be put behind the speakers with the pot pot
> > >nearer to my hand). Obviously no active devices (transistors, ugh!) are
> > >allowed because that would not be a potato amp but a hybrid amp.
> >
> > I'm curious about the 2V number. 'Consumer' line level is about
> > 316mVrms (I've also seen amps spec'ing 707-775mVrms) and Pro is about
> > 1.228Vrms so where does the 2V (rms?) come from?
>
> Yeah, right, I have a Velleman K4000 triple EL34 PPP I built from a kit
> that has 775mV rms as an input level. Someone once told us what it
> related to, but I can't find it now.
"775mV rms" is 1 milliwatt into 600 Ohms, or 0 dBm.
> 2Vrms is what my Quad 66 and 67 CDs put out. I've been told several
> times that most CD players put out 2Vrms.
Jon Yaeger
> Hi Andre,
>
> Thanks for the offer of the 7044 data sheet, but I have already downloaded
> one and so don't require another copy. The 7044 has lead me to another
> tube, the E182CC which appears to be even more suited to my needs, as the
> transconductance is 15,000 umohs while the trnsconductance of the 7044 is
> only 12,000 umhos. I am on the lookout to purchase some on eBay for my pp
> "potato" project.
>
> For the time being I have decided to go with a high impedance center taped
> choke for the phase inverter rather than a transformer as I don't have a
> suitable transformer in my junk box. I will keep my eyes open on eBay
> although the type of transformer I want is rare as hen's teeth and the
> best substitute goes for big money. Without the 1.5 step-up ratio in a
> transformer I will be down about 3 dB on sensitivity relative to your 417A
> "potato" amp.
>
> You didn't miss the class A design "specs." given by Patrick, he posted
> his piece on the 22nd IIRC, and you posted a message in response to his,
> so you should remember it.
>
>
> Regards,
>
> John Byrns
>
John,
Here is a link on tube headphone amps that you may be aware of. But if not,
it has some info that ought to help you with your project.
The first thing you'll see is a set of EC182CC curves . . . . .
http://www.headwize.com/projects/ciuff_prj.htm
Jon Yaeger
Andre Jute
post. -- Andre Jute
> --------------352BE55BF269A38999ADB65F
> Content-Type: text/html
> X-Google-AttachSize: 4074
>
> <!doctype html public "-//w3c//dtd html 4.0 transitional//en">
> <html>
> <tt>Here is a table of dissimilar triodes I included in the GA original
> article of 2000.</tt>
> <p><tt>Cheers, John Stewart</tt>
> <p><tt>TABLE ONE</tt>
> <p><tt>SUMMARY OF POWER TRIODES ACCOMPANIED BY</tt>
> <br><tt> A VOLTAGE AMPLIFIER</tt>
> <br>
> <p><tt>TYPE mu T1
> mu T2 T2 WATTS BASE
> CONNEXION</tt>
> <br>
> <p><tt>6BL7GTA 15
> 15 10
> OCT 8BD</tt>
> <br><tt>6BX7
> 10 10 10
> OCT 8BD</tt>
> <br><tt>6CY7
> 68 5
> 5.5 MIN
> 9LG</tt>
> <br><tt>6DE7,10,13 17.5 6
> 7 MIN
> 9HF</tt>
> <br><tt>6DN7
> 22.5 15.4 10
> OCT 8BD</tt>
> <br><tt>6DR7,10,13 68
> 6 7
> MIN 9HF</tt>
> <br><tt>6EA7
> 66 5.5 10
> OCT 8BD</tt>
> <br><tt>6EM7,10,13 64
> 5.4 10
> OCT 8BD</tt>
> <br><tt>6EW7
> 17.5 6 10
> MIN 9HF</tt>
> <br><tt>6FD7, 13 64
> 6 10
> MIN 9HF</tt>
> <br><tt>6FJ7
> 22.5 15.4 10
> COMP 12BM</tt>
> <br><tt>6FM7,13,15 66 5.5
> 10 COMP
> 12EJ</tt>
> <br><tt>6FR7
> 68 5.4 10
> MIN 9HF</tt>
> <br><tt>6FY7, 15 65
> 6 7
> COMP 12EO</tt>
> <br><tt>6GF7,10,13 64 5.4
> 11 NOVAR
> 9QD</tt>
> <br><tt>6GL7
> 66 5
> 10 OCT
> 8BD</tt>
> <p> </html>
>
> --------------352BE55BF269A38999ADB65F--
Andre Jute
I hope you were being ironic, Iveson. We were there already. We are not
lost without Pinkerton. In fact, we are better off in his absence.
If you were not being ironic, this is the nadir of your arsecreeping of
losers on their way out with no way back in. You joined the communist
party after Gorby declared it dead, you were Pasternack's last
defender, you tried to bring Slimy Mike LaFever back to RAT, you even
tried engineer the return of "Nodding Dog" Vince Rhea, as if we don't
have enough little garage traders already.
Are you trying to get into the Guinness Book of Records? Perhaps as
Most Insensitive Person on Earth who isn't an Engineer?
Andre Jute
Andre Jute
John Byrns wrote:
> In article <1141188060.9...@j33g2000cwa.googlegroups.com>, "Andre
> Jute" <fiu...@yahoo.com> wrote:
>
> > Clearly, a PP potato is higher level of challenge than the single
> > triode or dissimilar triode SE amp model. The 7044 is a tube with
> > everything except reputation. If the name on the glass were Western
> > Electric, it would be famous and overpriced. I missed the specs given
> > by Patrick. This sounds like you don't have curves. The 7044 is a tube
> > for which it is ferociously difficult to get reliable and usable
> > information. But I now have a PDF (216KB) I can forward to you on
> > request, and I have taken out the curves and enlarged them to make them
> > more usable (416KB). I also have various published tables (2.6MB) I can
> > send if required. Just ask; no problem as I have broadband but I don't
> > just want to send stuff if it will clog up your coms forever.
>
> Hi Andre,
>
> Thanks for the offer of the 7044 data sheet, but I have already downloaded
> one and so don't require another copy. The 7044 has lead me to another
> tube, the E182CC which appears to be even more suited to my needs, as the
> transconductance is 15,000 umohs while the trnsconductance of the 7044 is
> only 12,000 umhos. I am on the lookout to purchase some on eBay for my pp
> "potato" project.
This is an interesting choice. I thought about mentioning it but
decided it isn't worth mentioning such a rare tube; I tried to find
some last year or the year before and had no luck. I first heard about
the E182CC from Simon Shilton, the British designer of transformers and
amps for several manufacturers and under his own name. About ten years
ago Simon gave me at least half an hour on the phone about its merits.
Simon is keen in his experiments (like me, Simon' builds amps quite a
bit more conservative than his talk and his experiments) on overdriving
harmless, innocent little tubes, so whatever he likes is likely to be
very sturdy indeed.
> For the time being I have decided to go with a high impedance center taped
> choke for the phase inverter rather than a transformer as I don't have a
> suitable transformer in my junk box. I will keep my eyes open on eBay
> although the type of transformer I want is rare as hen's teeth and the
> best substitute goes for big money. Without the 1.5 step-up ratio in a
> transformer I will be down about 3 dB on sensitivity relative to your 417A
> "potato" amp.
> You didn't miss the class A design "specs." given by Patrick, he posted
> his piece on the 22nd IIRC, and you posted a message in response to his,
> so you should remember it.
Yeah, right, his piece on power from Class A. I thought you meant he
wrote on the specifics of the 7044 or some other tube then under
discussion. I have it now.
> Regards,
>
> John Byrns
>
> Surf my web pages at, http://users.rcn.com/jbyrns/
Andre Jute
Iain Churches
"John Byrns" <jby...@rcn.com> wrote in message
news:jbyrns-0103...@216-80-74-141.d.enteract.com...
I have a Studer D730 CD player (2V output)
http://www.kolumbus.fi/iain.churches/Pics/StuderA730open.jpg
plugged straight into my 50W PPP EL34 amp, which has
input sensitivity of 0dBm (775mV into 600 Ohms) balanced.
The amp has stepped attenuators on the input. These are
usually set at about 2 o'clock so this combination of output
level and input sensitivity seems about ideal.
Iain
Stewart Pinkerton
>Ah, thank you. dBFS is what I suspected. Yes, that would mean it's the
>headroom and even more critical than for analog because there's no
>analogous 'soft clipping' to it; there just ain't no more bits left to
>digitize with past that point.
>
>> but
>>several 'high end' players and DACs put out considerably more for some
>>reason. The lower voltage on the Quad spec will relate to the average
>>output level of a (probably classical) music CD.
>
>Well, if the 2Vrms is dBFS then I'd think the 316mV would be the
>nominal level one should design because if you used 2Vrms you'd have
>no headroom at all.
I'm not quite sure what you're getting at here, but you should
*always* allow headroom. Any integrated amplifier or preamp designed
to accept a 2V rms signal should certainly be able to accept at least
5V rms in the stages prior to the volume control. Naturally, if the
volume control is right at the input, common enough in valved
amplifiers, then the concept of 'headroom' is essentially meaningless.
If you're suggesting that amplfier should be sensitive enough to
achieve full output from a 300mV signal, then I might agree if you
wish to be certain of the ability to achieve clipping even from a CD
recorded at a low level. My own system is set to clip with a 1V rms
input, leaving 6dB of 'headroom' in this sense.