Congested ! 6CA7 Candidate ??

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by alanfc, Nov 13, 2005.


  1. alanfc

    alanfc Member

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    thats the only way I can describe it :(

    Now that I have better ears this is what I'm hearing.
    Rivera R55 into 2x12 (v30-G12h30) partial open back
    Power EL34 Winged C's.
    Strat with JB Jr. bridge (ceramic mag), pickup height 1/8" off strings.

    at full band volume, 'hard rock' slightly 80's/sorta EVH tones.

    one minute I'm turning down the mids because it sounds boxy and congested, then I turn the mids back up because I'm getting no bark. But then its harsh and congested.
    I had an EQ pedal in the loop but the poles aren't affecting what I want....

    Am I a candidate for : 6CA7's ?!?!? ? ?

    is it the partial open back cab? Should I seal it?
    The ceramic magnet pickup.? (I loved my Alnico 2 Custom Custom in another guitar)

    OR, am I wanting a 6L6 powered amp. I hope not !

    thanks for your diagnosis
    :)
     
  2. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    IME, 6CA7s have a much flatter response than EL34s. You can get a duet of EH 6CA7s for about 25-30 bucks. I think the EH version retains more EL34 character than the much more expensive GT version. Worst case is you have an inexpensive set of backup tubes.

    Though the open-backed cab might be contributing to the boxiness, putting it all the way up against the wall might give you an idea of the effect of the open back.
     
  3. alanfc

    alanfc Member

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    OK thanks guys

    Old Tele man, is this some sort of amp tech inside joke? !
    :D
    I'll look up this tetrode pentode business.
    I know on paper the US-Euros are similar but I 've always read they're difference to the ear..
     
  4. UfoPilot

    UfoPilot Member

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    Acording to EH it is a tetrode. Here is a quote from thier web site.
    Designed to the exacting specifications of the Phillips 6CA7. This classic tetrode returns to life in a big bottle design. The 6CA7EH is built to withstand today's high-gain amps while still retaining the detailed tone and component integrity of the original. A direct replacement, with military reliability, for any EL34.
     
  5. alanfc

    alanfc Member

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    OK thanks:)
    Would I have to take the amp in for a re-bias if I went from the EL34 to 6ca7?
    thanks
     
  6. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    Yup. It's just like any other tube replacement. Scott P and I have both run 6CA7s in our Riveras and have had great results biasing them relatively cold (32-35 mA). YMMV but there's some very good tone to be had without cooking the tubes.
     
  7. alanfc

    alanfc Member

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    OK thanks,
    at my last checkup my bias on the EL34's was approx 34-35 I remember,
    Do I still need to take it in for re-bias?
    My tech is great but in very high demand:(
    Thanks
     
  8. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    It should be re-biased. It's probably okay but...

    Frankly, I'd suggest buying a bias meter (e.g., Weber Bias-Rite) and DIY. It's not hard if you don't mind pulling the chassis and allows for immediate gratification in terms of tube swaps and tube replacement. Between the time and $$$ saved, it's money well spent, IMO.
     
  9. alanfc

    alanfc Member

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    thanks,
    I'm always thinking about doing this but never do it:rolleyes:
    I think I have some motivation now.
     
  10. UfoPilot

    UfoPilot Member

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    I agree. Get a bias meter and do it yourself. It's easy and you can tweak the bias for the best sound.
     
  11. Erik

    Erik Member

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    I'll third what UfoPilot and Alec have said.
     

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