Gibson Minuteman GA-20RVT

[Roland]

Just wondering if anyone has managed to get some reasonable tone out of one of these Amps?

Any and all help would be appreciated.

Mine is fully functional but very "sterile" to put it mildly.
All stock with new caps and tubes an upgraded speaker that helped a tiny bit, but still no cigar.
Recently inserted a 12AT7 in position V5 that added a bit of gain but also increased the noise level.
Bass control is reasonable and tight but it falls apart above that. Missing Brightness Sparkle at moderate volume.

Thank you in advance.

[Enzo]

Some people like this stuff. I have to admit that to me personally I have never heard one of the old Gibsons I thought sounded worth a damn.

Yes, I know that is not very helpful.

[Bruce / Mission Amps]

Some people like this stuff. I have to admit that to me personally I have never heard one of the old Gibsons I thought sounded worth a damn.

Yes, I know that is not very helpful.

THANK YOU!! I have players bring me these turds all the time and want me to tweak them up 'cause it's "vintage tube amp" and you know what all you can do with a turd.

[imaradiostar]

I've played a few at the Tinicum Guitar Barn and thought they were OK- they do one basic sound and it's not super impressive. The one I played had a neat distorted tone that seemed to vary texture but not brightness as you changed the tone control. I'd record a song or two with it but I wouldn't gig with it!

There is a lot of goofy filtering in the preamp. It would be easy enough to bypass most of it and maybe add a simple tone stack just to see it the amp comes to life at all.

The transformer PI isn't normally bad sounding- it must be the preamp that makes these suck.

jamie

[Roland]

My thoughts exactly about the tone stack and those funky filter networks.
Has anyone messed with those?

There must be a way to get some sparkle out of this muddy amp.
Everything above the bass is muffled until the volume levels are way too high....
and then it starts to show some potential but garbled mids and lack of brightness prevails.



Circut attached for reference.

Thank you

[Sweetfinger]

Some people like this stuff. I have to admit that to me personally I have never heard one of the old Gibsons I thought sounded worth a damn.

Yes, I know that is not very helpful.

While Fender stayed with the same sort of circuits throughout their lines, like the familiar tone-stack and tube complements, Gibson seems to have changed everything about their amps about as fast as they could work up to production. As soon as its going out the door, time to change it! That's why there are a lot of half-baked Gibson amps out there, but there ARE some good ones, too. I had a GA-20 that was a pretty sweet amp. I just recapped a GA-5 Skylark that sounded pretty nice, although it is kinda hard to screw up what is essentially, a Champ.

My main beef is those cardboard multi-section E-lytics that Gibson seems to have been fond of. Yuk. Oh. . . .and the weird-o tubes.

[dkevin]

Gibson Woes

I am in agreement with the frustration expressed about Gibson amps. Having seen some of the strange (not necessarily wonderful) things they constructed, I can understand the opinions. I think that they tried to be a bit too clever for their own good and progressively ruined their products. For example, the 50's tweed and two-tone amps are as straight-forward as an amp can be. I own several of them and they are so simple/ yet sound so good! As the 60's approached the external changes signalled major changes in the circuitry as well. The using of different tubes (6EU7/6AQ5) is not what ruins it in my opinion. They insert strange filters (as previously mentioned) that rob tone/volume and the amps sound thin and piercing when driven. These Crestline amps can be optimized, but not without making changes to the original design. Most of the wiring is still point to point.
The white-panel amps are definitely a mixed bag. Here, we find driver transformers and yet thinner tone. There are a few amps that seem to defy the trend but they are in the minority. It seems that with the drive for increasing complexity, Gibson had difficulty keeping their eye on the prize(balancing power with taste).
The Medalist amps (vertical control panels) don't have many fans. They are full of surprises.
I am not a professional amp tech, so I am looking at Gibson's gaffes from a different point of view. I don't have to try to diagnose and repair them with one eye on the time clock. It just makes me sad that they squandered their amp-building reputation. I love their use of different tubes and willingness to walk another road besides Fender's road. I don't love any of these amps (left pure-stock) as the Crestlines replaced the tweed amps.

[bret]

I have three of these amps and love them. I generally play one of four guitars through it. Early 1960s Gibsons with P90 pickups. This particular amp seems to prefer P90s as opposed to humbuckers or Fender pickups. I believe this is because P90s seem to force gain effect to these amps . That being said one could try swapping the 12au7s tubes for 12ax7 or 12at7s. I believe the 12ax7 will produce the most gain IMO, they are used in quality gain pedals. The 12au7s were originally designed for high end stereos where clarity was preferred. And that being said my first of these had a Celestion ceramic 70 watt speaker in it instead of original CTS speaker, a poor choice for an amp of this size. Replaced that with a Celestion 15 watt alnico Bluedog. I love this sound.