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"improving" a guitar amp

Discussion in 'Amps and Cabs [BG]' started by paganjack, Sep 2, 2008.


  1. paganjack

    paganjack

    Dec 25, 2007
    Los Angeles, CA
    so i know the old 'can i play bass through my guitar amp' question has been done. this is not that question. if this question has been answered before in detail i couldn't find it.

    i have a vox valvetronix ADVT-15XL. 12ax7 tube preamp, solid power amp, 15W amp, 10" speaker, closed back. It's a really nice small guitar amp, surprisingly loud too. I have been using it for quiet bass practice, and it sounds OK, but when i run the line out to my mixer, and hear the amplifier's tone w/o the speaker, it's really really nice. super punchy, nice and tubey.

    so i was wondering about the speaker. I know that if you run your bass through the guitar amp, supposedly the only spot that you can seriously damage is the speaker itself. So, could i put in a 10" full range/bass speaker and have a sweet combo amp that works about as well for either instrument? will a new speaker sound way worse for guitar? what sort of wattage would i want to shoot for for the speaker [it's a 15-watt amp]? i guess the enclosure size might not be optimized for bass, but has anyone else tried this? is it worthwhile, or a waste of time and money?
     
  2. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    The size of the enclosure, combined with the closed back, mean it will sound very poor at any "real" volume. If you want a project, remove the amp from the combo and build a little housing for the amp part by itself. Then use it with a real bass cab, or send the line out to a large powered monitor or powered bass cab. Oh, and be sure to use some sort of load on the amp if you only use the line out.
     
  3. paganjack

    paganjack

    Dec 25, 2007
    Los Angeles, CA
    hmm...i'm pretty awful at woodworking, and i do want to retain it's functionality as my guitar amp too. Since I was only planning on using it as a small practice amp, i think that it's too early to start ripping it up that much. [it's still fairly new, so maybe someday i will want to try this anyway]

    thanks for the response, bongomania!
     
  4. xampworshipx

    xampworshipx

    Jul 13, 2008
    Someone correct me if i'm wrong here, but if this amp has an extension speaker jack, you could theoretically go in the back, disconnect the speaker that's already in there, and plug the thing into a bass cabinet. Voila, loud operating volume without damaging speakers.
     
  5. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Sounds right to me.
     
  6. paganjack

    paganjack

    Dec 25, 2007
    Los Angeles, CA
    it doesn't have an extension speaker jack, unfortunately, otherwise I totally would have done just that.
    I'm more concerned about speaker blowout than sound- it's not ever going to be super loud unless i absolutely love it.
    I guess I'm still curious- would putting a different speaker in it prevent this problem, and still sound OK with both bass and guitar?

    Or, how hard would it be to make a speaker cab jack for it? maybe even a switch to go from external/bass speaker to the internal guitar speaker? could i just hijack the speaker wires and put a switch assembly in the line, or would it take more than that?
     
  7. xampworshipx

    xampworshipx

    Jul 13, 2008
    oh, also, some tips:

    UNPLUG IT FIRST (can't stress that enough)

    and disconnect the wiring from the unit, not the speaker itself, tubes get pretty angry if they're trying to feed power to something that isn't there.
     
  8. xampworshipx

    xampworshipx

    Jul 13, 2008


    that is a very good question that I don't have an answer for. Now i'm curious too.
     
  9. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Perfectly reasonable to put a switch in there. Just make sure the switch has a sufficiently high power rating.
     
  10. the tube is in the preamp only, so disconnecting the speaker should not be a problem.

    a 10" fullrange speaker for bass wont be nearly as sensitive as the guitar speaker in there (you will sacrefice the spl for low end) so it wont be as loud, and the amp wont be able to amplify as much low end. the sealed back is a good thing. might be able to use the speaker in there if you dont turn up the bass too much, but you still risk blowing it from overexcursion.

    it wont be very loud, and probably not very low, but it will work. but a bass speaker wont be cheap unless you find a deal somewhere, and you might aswell buy a little combo that will work better.
     
  11. paganjack

    paganjack

    Dec 25, 2007
    Los Angeles, CA
    thanks for the input guys!
    i just might try to put a switch assembly in there when i have some time to mess around with it. i think that would be the best option- cheapest, fastest, least risky. if i do, i'll post some sound clips.
     

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