Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: chee16 on July 18, 2021, 10:06:02 am
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So let's see if I can do this right. I was asked to look over a qwirky little amp that was being sold. Thought it was interesting once I started looking at the circuit. I haven't powered it up at all, though I know the shop did to test it, said it was low volume and the trem didn't work. When I first looked in I thought it would be fairly typical based on the tubes, 12ax7 x2 6BQ5 x2, but it's not. Any ideas or info you guys might have is just for fun and the sake of interest. I have been asked to make it function like it would have new, and since it looks like very little has been done to it, that shouldn't be hard. I think the ext speaker jack was added, and there is an orange drop from volume to tone pot that is probably new. There is marker on the inside of the chassis "1161", obviously no idea if that has anything to do with the date. Speaker (Jensen Special Design) cone is stamped C0-80X3, magnet stamps C8U-3230 EXL1
If nothing else, it's neat to look at. I drew out the schematic, sorry I haven't drawn a ton, so I spaced it out more then needed, hope it's easily read.
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Think I have it now, more pics here.
Thank you for the help!
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Maybe this will help?
https://el34world.com/Forum/index.php?topic=16961.0
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Crud, in my reading on how to post pics, I mixed up the pixel size, thought it was 1600. Let me try again. Sorry. I swear I tried, honest.
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First thing that struck me, on V1, the anodes are connected, as are the cathodes, then each goes to a 150k resistor, and are connected together. But there is no high voltage at all in V1.
V2B would the be oscillator for the tremolo? V2A would be the only gain stage?
It's neat, but there might a reason this design was never copied? Or was it and I just don't know, haha.