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Old 18th October 2003, 01:19 PM   #11
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Quote:
Originally posted by TugaTweaker
It seems hard work is needed . I think i will look for the 211 or
845 instead .
Don't forget the GM70
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Old 18th October 2003, 11:42 PM   #12
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GM 70 . This one ? http://www.nhcbrenners.hu/ It seems good to me , but no component values in it .
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Old 19th October 2003, 12:12 AM   #13
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Quote:
Originally posted by TugaTweaker
GM 70 . This one ? http://www.nhcbrenners.hu/ It seems good to me , but no component values in it .
That was in Glass Audio in 2000 or 2001.
Seems waaaaaay too complicated for a relatively easy to drive (for a bright emitter) tube.

I played with the GM70 a lot over the last year, with a lot of different drivers, incl 300Bs, and the best driver I found was a 12HG7A in pentode. Made a very clean two stage amp and the driver tubes cost $US 0.70 each.

GM70 datasheet

Take a look at these for some of the inspiration I found to do this
Similar 813 amp
Pentode test data
Legacy amp

Lots of people won't try this because they don't "beleive" in pentodes (I was one of them) but for the cost of the tubes involved, and there are others applicable such as the EL84, SV83 and 6AQ5, C3m etc, I'd strongly suggest giving it a try.
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Old 19th October 2003, 12:47 AM   #14
grataku is offline grataku  United States
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Hey Brett,
what's the source of the 805 schematic you posted earlier?
I seem to recall it is a classic japanese book...is it still printed? I'd like to get it.
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Old 19th October 2003, 12:48 AM   #15
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Brett , thanks for the nice links , they deserve careful reading .

Cumps

TugaTweaker
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Old 19th October 2003, 05:24 AM   #16
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Quote:
Originally posted by grataku
Hey Brett,
what's the source of the 805 schematic you posted earlier?
I seem to recall it is a classic japanese book...is it still printed? I'd like to get it.
I found it online somewhere, but don't recall where exactly. I collect these sorts of things when I find them. Seeing as it's a WAVAC, I'd say the design was by Nobu Shisheido, and I'd suggest his book on Transmitter Tube Amplifiers.

I'm sure there are other sources, but try here , ninth item from top.
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Old 19th October 2003, 09:54 AM   #17
RS is offline RS  Germany
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Default Shishido design

Yes, the mentioned Wavac 805 is a Nobu Shishido Design. A lot of Shishido's Amp have the same features: Greinacher (voltage doubler) Power Supply, Interstage couplung with an "inverted" transformer, Class A2, overall feedback, and a feedback winding on the output transformer.
There are similar Shishido amp's with 801A, 811A, 826, 838.
Also there is a commercial amp with the 805 from Antique Soundlab, who is clearly based on Shishido:

http://www.divertech.com/explorer805dt.html

Regards

Ralf
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Old 19th October 2003, 06:17 PM   #18
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Default Re: Shishido design

Quote:
Originally posted by RS
Also there is a commercial amp with the 805 from Antique Soundlab, who is clearly based on Shishido:

http://www.divertech.com/explorer805dt.html

Regards

Ralf
Based on the quality of the ASL OPT's I had, I can't see it being remotely in the same league.
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Old 19th October 2003, 08:51 PM   #19
RS is offline RS  Germany
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Default ASL vs. Shishido

Quote:
Based on the quality of the ASL OPT's I had, I can't see it being remotely in the same league.
I didn' talked about the amps, I only referred to the basic layout of the ASL schematic, which has a lot of the Shishido design: 12AX7 - 6L6 - IT - 805. Operating points are a bit hotter: 833V Ua, 140mA Idc and +28V Ug. Also it is using the Greinacher voltage doubler in the Power Supply.

Regards

Ralf
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Old 20th October 2003, 09:44 AM   #20
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Brett
i am also going with a pentode front stage but would be a 3 stage
6688 ----el34 cathode follower ---gm70
might go with a 2 stage but power would be lower (can it sustain A2 operation?). Probably try the fame c3m or the sv83
what's the specs for 12HG7A rp,mu ?
would look at pete millet's side if he has it
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