Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: BrianS on February 23, 2014, 03:01:50 pm
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Several years ago (5? 6? :dontknow:) I bought this Heathkit amp at an antique store. My thought was to make it into a guitar amp. Not knowing or caring much about some of the vintage parts inside (other than the tubes) I gutted it & chucked pretty much all the old components. My only concern at the time was that it had nice tubes, beefy looking transformers & a useable chassis. Then, as often happens with projects like this, it got shelved for about half a decade.
Now, I'm contemplating what I can do with this thing. I did a search & found one thread where someone rebuilt an A-9c into a guitar amp, but it seemed very troublesome & the thread was confusing to me. Basically it was no help.
So, I'm either going to rebuild this back to original specs (It came with original owner's manual/instructions/schematic), or turn it into a guitar amp. I'm looking for suggestions, experiences, advice, etc...
Thanks
(https://lh6.googleusercontent.com/-lXAO0EKtNhU/Uwpem40Ei4I/AAAAAAAABXM/wXTwTaExK6g/s640/003.JPG)
(https://lh5.googleusercontent.com/-yiEmOKXbEu0/Uwpedu3QatI/AAAAAAAABXE/2GyIzeIFj5o/s640/002.JPG)
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Now, I'm contemplating what I can do with this thing. ...
You might build it back into what it was, a hi-fi amp.
You might build it back like it was, but adapt for guitar use. According to the sensitivities listed (http://www.hifiengine.com/library/heathkit/a-9c.shtml) for each input, the Mic & Moving Magnet (MM) inputs would be a bit too hot, while the Ceramic input would be a bit too clean. I'd leave the last 12AU7 and the entire output stage the same (as well as the power supply), then look at what you might do with a 12AX7 and 12AU7.
The original tone circuit is likely useful, but will probably need values changed to work best for guitar.