Preamp tube advice?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by leftyvic, Jul 17, 2008.

  1. leftyvic

    leftyvic Member

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    Hi folks ... I know next to nothing about tubes, let me say that right off the bat.

    I have a Groove Tubes Trio preamp, which is a nice little piece with three channels. In my working band, I primarily use the Clean channel, which is a blackface Twin style circuit, designed to have nothing but headroom. GT advises running both gain and volume wide open at all times.

    Right now, it's very clean but a little too sterile; I'd like to warm and fatten it up a bit, maybe just a touch of overdrive available, better lows. Is there a preamp tube that is reasonably priced and easily available I might try in there? I know there are some reissue tubes being made now that are supposed to be pretty good.

    Not looking for expensive vintage stuff, though!

    Thanks!
     
  2. Blue Strat

    Blue Strat Member

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    I'd start by tweaking the controls first or using one of the higher gain channels. A tube swap in the clean channel isn't likely to make it much dirtier.
     
  3. leftyvic

    leftyvic Member

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    Hmm ... the voicing I want is the Clean channel voicing, the others are too dark or high gain to get a Fender Twin sound. I just want it to break up a little bit.

    I thought it could be adjusted with different tubes, because I had a second Trio for a while and the output was much dirtier, had a really nice subtle creamy overdrive on the clean channel with the gain up all the way.

    I was able to A/B both Trios through the same setup and the difference was very obvious.
     
  4. Blue Strat

    Blue Strat Member

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    Do you happen to know what tubes were in the Trio you liked better?
     
  5. leftyvic

    leftyvic Member

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    I wish I did, Mike ... I am fairly certain they were Groove Tubes tubes, though.

    I appreciate the input.
     
  6. Blue Strat

    Blue Strat Member

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    If the units were drastically different I suspect that there was a difference in the units or a VERY weak tube in one of them.

    The NOS RFT 12AX7 might be something to try.

    Not sure how those units are wired, but if the preamp tubes share a cathode resistor/capacitor, pulling one of the other channel's tubes would make the remaining tube in the combo break up earlier. Can't hurt to try.
     
  7. rockon1

    rockon1 Member

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    Could try running a hotter signal into it. My lowly SD pick up booster pedal is a fairly uncolored(to my ears)clean boost and can really make a guitar signal HOT. Makes any clean channel break up earlier. Bob
     
  8. Gargoyle

    Gargoyle Member

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    +1 on the RFT's, well priced for a NOS tube. I found you gain a warmer quality without losing definition. I found the New prod Tung Sol 12ax7 to be low noise and quite warm sounding too.
    I had a trio of EH 12ax7's in an amp I purchased about 6 months ago, same deal as your GT's, low on noise but also, low on character.......... they are now sitting in a box as spares.
     
  9. VikingAmps

    VikingAmps Member

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    I think some of the early Groove tubes were RCA, but they used a lot of different manufacturers. If you're looking for a Twin sound that would be a good one to try too.
     
  10. Blue Strat

    Blue Strat Member

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    Early GT's could have been almost anything.

    RCAs are good for a Fender sound but not particularly good for early breakup which seems to be the important detail in the OP.
     

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