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So this has a bit of a backstory: I played an old blonde ~1960 Gibsonette parallel single-ended amp at a guitar show a few months back, and loved the hell out of it -- but the seller wanted what I considered an exorbitant price, nearly double what they were selling for a couple years ago.
I'd been studying amp design & maintenance / building for a while and had learned almost enough to hurt myself (OK, I'd actually done a couple of mods to my Princeton Reverb without self-electrocution), and so I got the idea that the Gibsonette circuit was simple enough that I could probably attempt a build. So I started looking at designs.
Then, I happened upon two things: (1) a Hammond AO-39 power amp chassis out of an old A-100 organ (2 - EL84/6BQ5 in P/P) for a decent price, complete except for tubes; and (2) a cache of Russian 6P1P-EV tubes -- which are supposedly very similar to 6V6s, but with lower plate/screen voltage ratings (actually very close to 6AQ5W) and they use a 9-pin socket like an EL84. Best part: they are available in bulk lots on eBay from the Ukraine for about ~$2.50 - $3 per tube, including shipping -- so I got 30 of them, which may be about a lifetime supply.
So I got a GA-8 Gibsonette schematic and a 5F2 Princeton layout diagram and started putting together a layout diagram to fit it all into the A0-39 chassis, which has a little bit of a funny configuration compared to guitar amps (see attachment). I had it nearly complete -- and the only other thing to do was to figure out the tranny specs and how to reconfigure the voltage divider network for the 6P1P voltage requirements before I started actually building it. I even started gathering resistors, fuses, power cords, and other parts. The idea was going to be to build it as a head and stuff it into an old antique tube radio cabinet from the 30s, because I think those look cool. Hadn't even started to tear the old components out of the Hammond chassis to begin the build, when ....
I found a ~1959 Gibsonette, complete, recently serviced and in good working order, for less money than I ever expected to pay for one. So I bought it, of course.
But now, what to do with my project? I was kind of excited to do a build, but frankly, I also know it would take a hell of a lot of time that I'd probably rather spend playing. So I could:
- Complete the build anyway, as a learning exercise and to have a second, cool, amp head, even if it takes me months to complete and I've already got more amps than many people would consider sensible;
- Sell off the components separately, so a Hammond enthusiast can restore an organ and someone else can make use of these oddball Russian tubes for another project, etc.; OR:
- Sell off everything together as a partial project "kit," together with the schematic and partial layout, to help someone complete what I almost started.
What do you think? Anyone interested in this kind of a project or have another use for either the Hammond chassis or the Russian tubes? Or want my in-progress layout diagram to complete or modify?
I'd been studying amp design & maintenance / building for a while and had learned almost enough to hurt myself (OK, I'd actually done a couple of mods to my Princeton Reverb without self-electrocution), and so I got the idea that the Gibsonette circuit was simple enough that I could probably attempt a build. So I started looking at designs.
Then, I happened upon two things: (1) a Hammond AO-39 power amp chassis out of an old A-100 organ (2 - EL84/6BQ5 in P/P) for a decent price, complete except for tubes; and (2) a cache of Russian 6P1P-EV tubes -- which are supposedly very similar to 6V6s, but with lower plate/screen voltage ratings (actually very close to 6AQ5W) and they use a 9-pin socket like an EL84. Best part: they are available in bulk lots on eBay from the Ukraine for about ~$2.50 - $3 per tube, including shipping -- so I got 30 of them, which may be about a lifetime supply.
So I got a GA-8 Gibsonette schematic and a 5F2 Princeton layout diagram and started putting together a layout diagram to fit it all into the A0-39 chassis, which has a little bit of a funny configuration compared to guitar amps (see attachment). I had it nearly complete -- and the only other thing to do was to figure out the tranny specs and how to reconfigure the voltage divider network for the 6P1P voltage requirements before I started actually building it. I even started gathering resistors, fuses, power cords, and other parts. The idea was going to be to build it as a head and stuff it into an old antique tube radio cabinet from the 30s, because I think those look cool. Hadn't even started to tear the old components out of the Hammond chassis to begin the build, when ....
I found a ~1959 Gibsonette, complete, recently serviced and in good working order, for less money than I ever expected to pay for one. So I bought it, of course.
But now, what to do with my project? I was kind of excited to do a build, but frankly, I also know it would take a hell of a lot of time that I'd probably rather spend playing. So I could:
- Complete the build anyway, as a learning exercise and to have a second, cool, amp head, even if it takes me months to complete and I've already got more amps than many people would consider sensible;
- Sell off the components separately, so a Hammond enthusiast can restore an organ and someone else can make use of these oddball Russian tubes for another project, etc.; OR:
- Sell off everything together as a partial project "kit," together with the schematic and partial layout, to help someone complete what I almost started.
What do you think? Anyone interested in this kind of a project or have another use for either the Hammond chassis or the Russian tubes? Or want my in-progress layout diagram to complete or modify?
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