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In Reply to: RE: Harvard Electronics H-1 OTL Amp posted by mrflex65 on February 12, 2016 at 11:10:08
Back in about 1979 Julius made me a direct-drive amp to power my STAX SRX ESL headphones. I don't know if it is one of a kind or not. JF also hand-drew the schematic for me. (You're right, Lew: he was a nice guy.) The combo is still sensational. I will never part with the amp or the schematic. Call me sentimental . . .
Follow Ups:
Perhaps a coincidence: In 1979, he made me a pair of H3aa monoblocks. When I went to his "factory" (one or two rooms on 72nd St, west of Broadway by a few hundred feet) to pick up my amplifiers, he was building an OTL headphone amplifier for someone. He was rather excited about it and showed it off to me. I have to wonder whether that was your amp, Chuck.
He made his own transformers, and the place reeked of tarry odors, probably toxic.
LEW, wouldn't that be amazing!
I never visited JF's "factory," but I had a number of very pleasant conversations with him
Banat,your welcome! All the output tubes check fine,one of them has lost most if not all of the getter flash.The input fuse has blown,but doesn't appear to have been a "catastrophic" event.All the fuses look to be original to the amp as well.The person i bought this from cleans out old houses and this is what he found....
mrflex65I think that 12B4A power triode which looses almost all getter have to be replaced with fresh one , just to attain future stable balance of output SEPP power stage for next period of amp use ,
but there is so many other things that have to be Very Very Carefully checked and examined before that old H1 will be again in power on condition , and ready for use , it is so old ,
and check that old power cable since from your pics seems to me that it is in not so good condition at place of trough chassis input plastic receptor ,
and if is possible add some more pics , especial from under the chassis ,
and one question , did that person from which you have bought this amp have maybe one more H1 ? , since it will be cool to find another one for your stereo system use ,
anyway is great thing that you have recognized and saved very significant piece of audio amp history .
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"Art which does not have the appearance of art is true art."
- Old Roman saying -
Edits: 02/13/16
I believe that this schematic is very close to Harvard Electronics H1-OTL amp,it is extracted from oct.1956 article ,
-A Practical Commercial Output Transformerless Amplifier - by Julius Futterman .
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"Art which does not have the appearance of art is true art."
- Old Roman saying -
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