Make a bass pre-amp from a guitar amp?

Discussion in 'Amps and Cabs [BG]' started by groov'ster, Aug 30, 2005.

  1. Along time ago I used to play the g****r and used a small practice at home. When I started playing the bass I once again used the same amp for my practice amp. I get an awesome clean sound and tone from the amp and am considering turning the amp into a pre-amp for my main rig.
    The amp is only 15 watts, has no external out(s) except for the headphone. I am going to see if that (headphone) will work going into my main head as a pre-amp. If it DOES NOT how could I wire it up to use it as a pre-amp?
    Would 15 watts be enough to send to my main head?
    Currently I only turn it up about halfway to get the sound so that would be about 6-7 watts, would that be enough?

    Any suggestions?
  2. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    do NOT run the speaker out jack of your little amp into your head!!!

    the headphone out should work decently well...

    but- you should consider building a load box for the little amp with an actual DI.

    actually, if this is a solid state amp, you could build a simple lineout with just a speaker and likely run the amp without a load.
  3. There are cheap little things around, like the behringer DI, that can handle power amp outputs. Then from there to your head.
  4. It only has the headphone out, not a speaker out.
    It is solid state though.

    Forgive my ignorance in this area. but if I hear you, what you are saying is to connect a DI to the amp that would run to the head.
    How / where would I get the signal from the amp? Should I make a 1/4 jack from the Speaker wires of the amp or should I catch the signal from the internal componets of the amp?
  5. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    The headphone output is NOT an instrument level input that your other amp is expecting. It will be too hot, and it could possibly fry the input section of your other amp. That's why the other person recommended putting something before it to absorb the load and keep the level down.

    The one thing you should NOT do is wire a jack to your speaker wires and connect that jack to the input of your second amp. That will fry it for sure.

    Frankly, this is all a bad idea. Get a proper preamp or something like a Sansamp BDDI (used for around $120) and do it right.
  6. Here's the di thing:

    "Go ahead and plug that guitar amp's speaker output into the ULTRA-DI—it’ll deal with ratings of up to 3,000 Watts and give you a perfect signal at the other end."

    Always fun, playin' around. I once had a peavey bandit guitar amp for a while, liked some sounds my bass got out of it... No match for the real thing, off course :p

    Attached Files:

  7. Oh trust me, I ain't fryin anything cept chicken!

    I'm looking at this like an experiment of 'could it be done'. I already have plans to get an Avalon U5, but I am always tinkering with stuff.

    My head will accept a pre-amp input on the rear control panel. But I began to wonder about this as a low cost option because it has such a good sound to it. It might give a completely different sound when running through a 4*10 cab but I don't know unless I try.
    You mentioned the peavey amp...well this is a peavey rage 158. 15 watts into a 8" spkr.
    I'm also gonna get with the local amp doctor to find out about it also.

    I'll post the results when / if I do it.

    Thanks for all the info guys.
  8. Matt H

    Matt H

    Jul 30, 2005
    Ithaca, NY
    that's a bad and misleading description... just because the DI claims it can handle amps that push 3kW... you still need a load... (well, that is, for tube amps that require a load)

    but the most basic DI is just a pair of resistors, some will even have a cap (not a bad idea). Look for a schematic of a Matchless Lightning, or similar small matchless amp, to see how they get their line out. if i remember correctly, it's just two resistors and the jack.

    the easiest way to do this is just to tap it in right off the speaker terminals... but you might want to build a discreet unit. or just buy the behringer thing.

    but the dI boxes don't give the amp a load- a fact they like to downplay.