When Is Gibson Not A Gibson?

Discussion in 'Project Depot' started by andrewsrea, May 22, 2019.

  1. andrewsrea

    andrewsrea Well-Known Member

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    @golem brought his 1967 GA-35 to me in January, barely running and sounding like crap. Then I told him to go watch Youtube videos on GA-35's - they all sound like crap. They were designed by hearing-impaired engineers. I am surprised these were in the Gibson catalog as long as they were.

    He gave me carte-blanche to redesign, with the desire to make it Fender Deluxe Reverb like. It ended up even better: a 1964 Deluxe Reverb, meets a 1957 Tweed Deluxe, meets a Fairchild inter-stage (it has a transformer inverter, which drives the power tubes).

    Channel 1 is more scooped like a FDR. Channel 2 is Tweed with lush spring reverb & vibrato. Replacing the 12AU7 driver (V6) with a 12AT7 you loose the vibrato, but gain really awesome harmonics from the inner-stage transformer.

    There is not much of the original circuit that is left, nor copying Fender, etc. It is more my own design than those it sets to emulate (I actually had to draw a schematic to ensure it could be repaired in the future). Replaced the speaker with an early 80's Pyledriver 12", new reverb transformer and tank. I used many of the original RCA 9-pin tubes and converted the output tubes from 7199 to 6V6. Although, it is set up to also use: 6L6, EL-34 & 6550s.

    This is probably the best single 12" combo amp I've ever heard. It really gives back to the player and is very pedal friendly. It is loud enough to be used with a drummer, but not ear splitting. The exterior came out nice as well (vinegar wash - black shoe polish finish!). 20190521_184140.jpg 20190521_184215.jpg
     
  2. golem

    golem Well-Known Member

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    I'm a little confused about the vibrato. Which tube did you end up using? Or did you find away around that issue.

    I'm super excited to come by, try it, and bring it home!
     
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  3. Razzle

    Razzle Well-Known Member

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    Kudos to you @andrewsrea !

    How about a clip?!? (against another amp)
     
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  4. RockYoWorld

    RockYoWorld Well-Known Member

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    Basically, if I read that right... You pretty much just designed your own amp and put it in a crappy Gibson's body (the amp being crappy, not the body, necessarily)? COOL BEANS! I, too, want sound clips. I'd also like a bit of your smarts and experience. That's just gosh darn cool that you can do all that.
     
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  5. Mickey

    Mickey Gandalf the Intonationer

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    HEY! DUDE! I played a lot of gigs with that amp back in the 1960's! :)
    GA35RVT that is. "Invader"
     
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  6. andrewsrea

    andrewsrea Well-Known Member

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    If you use the 12AU7 in the V6 spot, the Vibrato works and it sounds really good. Like a FDR.

    If you pop in a 12AT7 into the V6 spot, the Vibrato no longer works. But it sounds monstrous. Worthwhile tradeoff, IMHO.
     
  7. andrewsrea

    andrewsrea Well-Known Member

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    I'll try to get to one this weekend.
     
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  8. andrewsrea

    andrewsrea Well-Known Member

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    Close - this is the GA-35RVT "Lancer". The "Invader" was a very good sounding Gibson amp. Most Gibson amps sounded pretty good, but this design was really sterile. Weird cap - resistor - cap networks going on.
     
  9. andrewsrea

    andrewsrea Well-Known Member

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    Here is the schematic:
    Golem GA35RVT 5-11-2019.jpg
     
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  10. andrewsrea

    andrewsrea Well-Known Member

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    Thank you and always happy to share what I know.
     
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  11. MarkW

    MarkW Well-Known Member

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    That’s a handsome amp, good job!
     
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  12. golem

    golem Well-Known Member

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    It definitely didn't sound great when I picked it up. But a few people mentioned this being a good platform to mod into a Deluxe Reverb. Deluxe Reverbs have a sound I really love, so I'm quite excited.
     
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