A tale of three Gibsons

[Rhodesplyr]

A client of mine handed me three Gibson amps, today, in various states of repair, asking for advice on "what to do with them."

One is a 1962 version of the Gibson GA-30 RVT Invader (circuit found on the Epiphone EA-12RVT schematic), and, from what I've read online, players seem to think very highly of it. This one has a 5AR4 rectifier and no 0A2 tube.

The second is a 1966 GA-20 RVT Minuteman, and reviews are mixed on this one. Most detractors blame its faults on the strange preamp circuit, and, looking at the schematic, I can see what they mean. I'm left wondering what the designers were attempting to accomplish. With five preamp tubes, it strikes me that it might be a good platform on which to build something known to work better.

The third is a solid-state G30 about which I can find little discussion.

I'm thinking of suggesting that we go ahead with a restoration of the GA-30 RVT, but I'm less sure what to recommend about the other two.

Any opinions?

[Jag]

I'd restore the GA-30.

I'd probably also restore the G30 just because I'm not really interested in playing or modding a solid-state amp.

What kind of shape is the GA-20 in. If it's pretty far gone, I'd make it into something else unless he wants to sell it. It doesn't sound like it's too desirable even if it were in mint condition.

[Chuck H]

Most of the less desireable Gibson amps become much more desireable once the funky T filter is removed or bypassed. I'd agree with Jag on this. But rather than rebuild the GA-20 I might only mod it a little. IMHE most of the old Gibson amps are capable of good tone once the preamp is simplified to be more like other typical guitar amp circuits.

[Rhodesplyr]

Thanks, Chuck.

I think we're basically on the same page. It wouldn't require that much modification to make the GA-20 into a more typical guitar amp. The only unusual thing remaining about it would be the transformer phase inverter, which I have no problem with in theory--other than the fact that it doesn't seem entirely necessary for an output stage like this one. I'm not sure what load it presents to the 12AU7 driver stage.

Did Gibson build many amps with a transformer PI?