Tube Amp Modifications

Discussion in 'Amps and Cabs [BG]' started by martens-koop, Feb 14, 2004.

  1. martens-koop


    Oct 10, 2002
    Hi there... I've got a 30 watt tube amp from the seventies (a garnet) and I was wondering if someone had any advice on modifying it... I'd like to remove the preamp section and use it to drive a solid state power amp. anyone ever done this before? or is the power amp / preamp section in a combo unit inseperable?

    I've never worked on tube amps before, but I've got a pretty decent knowledge of electronics, and my wiring / soldering skills are quite good. is this a project worth tackling or is it capitol s Stupid?

    thanks... jmk
  2. The 0x

    The 0x

    Aug 24, 2003
    Timonium, MD
    I'd keep it stock the way it is, and use it as a rehearsal/recording amp for when you want overdrive at a reasonable level. Besides, with tube amps, most of the tone comes from the power tubes.

    By the way, what's the model of the amp? I'd like to look into this amp.
  3. It can be done, but it's not worth doing. You would have to BUILD a completely new, separate power supply. At 30 watts, you could tweak the preamp and use it with a separate efficient cabinet for recording. The Ampeg B15N is only 35 watts for comparison.

    Tube amps can be dangerous, so I don't suggest you tackle a project like this alone without firsthand knowledgeable guidance from someone with experience.

    While power tubes certainly affect tone, it is an amp's preamp first and foremost, that controls most of how it sounds.
  4. bassmantele


    Jul 22, 2003
    Boston MA USA

    Gilles Garnet built some nice amps, so I wouldn't recommend tearing one apart just to scavange parts. You'd be better off selling the amp to someone who wants it as is, and building a preamp from scratch. The amp has one power supply for both pre- and power amp, so you would have to destroy the amp to use it as you describe.
    Check out the amp forum at for plenty of info on amp building.
  5. martens-koop


    Oct 10, 2002
    I'm not sure exactly what kind of amp it is... its got controls as follows:

    Speed (tremelo)
    Depth (tremelo)
    Footswitch jack in
    on / off switch

    its got a 15 inch speaker and tubes as follows:


    I paid about 200 bucks for it a while back. I'm hearing that attempting this is not a good idea... I was hoping that it would be a matter of just cutting it apart before the signal hits the power amp section... but oh well... BTW: the thing definately has two transformers... I'm asuming one is the power supply transformer and one is for the output transformer...

    anyways, talk to you later...

    when I used to live in winnipeg, I visited the garnet shop two or three times a year... (4 out of 6 rigs I've owned have been "his")

    His last name is Gilles, his first name is Gar (or at least thats what everybody called him) I believe that we prounounced his last name Gill-ease)

    take care...

  6. I agree with the others--why destroy a perfectly good vintage amp? Tube preamps are not terribly complicated, IMHO it would be easier to build one from scratch than it would be to cut up your amp. A single 12AX7 and a couple of tone controls--get a book like "The Tube Amp Book" which has a ton of schematics, and look at some of the simple circuits like the Harmony or Kay, or some of the early Fenders that don't have a reverb. And definately check out the link mentioned earlier to Ampage, and then do a search for other preamps...there's tons of good info out there.