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Old PA amp ---> New Bass Amp?

Discussion in 'Amps and Cabs [BG]' started by tornadobass, Mar 22, 2009.

  1. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    I have an old PA amp that runs four 6L6 power tubes and would like to re-do the preamp section into a one channel design that would be good for bass. I'm leaning toward something simple and Fender-like, with just treble, bass, and gain.

    Anybody done a project like this?
  2. seamonkey


    Aug 6, 2004
    A lot of old PA amplifiers were designed just for Plublic Address - just voice. The transformers may not have the frequency range to support bass. Make sure it uses tubes available today. Plan to change all the caps.

    I'd recommend picking up a demo of Peavey Revalver. You'll be able to build a virtual amp with different tone stacks or tubes and hear how it's going to sound before you go through the trouble of soldering.
  3. anderbass


    Dec 20, 2005
    Phoenix. Az.
    So what brand/model PA head are we TalkBassin here tornado?
    I used to have an older (un-modified) Fender PA-135 head that worked prety good for bass or guitar.
  4. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    We're talking older...Bogen, Masco...old school PA amps in gray metal boxes :hyper:
  5. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    The Bogens are much better suited to guitar.

    I've got an old Bogen Challenger 100w (7868s I think) that distorts way too much for bass.

    The output transformer is very small for a 100w amp, but as anderbass said, it wasn't pushing any low end.
  6. 18eranaRic

    18eranaRic Banned

    Mar 7, 2009
    Malibu, USA
    i had a Masco, it was really awesome for spongy power tube guitar, and even better with a harmonica and a green bullet. I was literally begged by a blues-harp guy to have it. not a lot of low end with bass, and really low wattage (i think it was like 25 watts or so)
  7. 62bass


    Apr 3, 2005
    I had a couple old Bogen's when they were new and one of the few PA amps available. Awful for anything but low volume voice and not too good at that even. Worse for guitar unless you wanted lots of distortion. Terrible for bass.

    You could do a lot better if you want a tube amp. Look around for an old Dynaco MK III or an Eico 60 watt hi-fi amp. They have transformers suited to bass. The very first Sunn tube bass amps were just re-worked Dynaco MK IIIs. I just sold a pair of Dynas a few months ago.

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