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Building my own preamp(s)

Discussion in 'Pickups & Electronics [BG]' started by PilbaraBass, Aug 8, 2005.

  1. I've just ordered some bits at Dick Smith (aussie version of radio shack, but much better) and am going to build some basic gain-only preamp circuits to put into a couple of my cheaper basses...I'm also planning on putting in a bypass switch...when I'm done I'll post a clip A-B'ing the results...

    my goal is to get a little more "beef" from my beast.

    I have found that I can build pre-amps quite inexpensively and I want to experiment a bit.

    Anyone tried building their own pre-amps, and what were your experiences?
  2. utopia_imminent


    Jun 19, 2004
    i have done one before but the thing is hissy. so, i chucked aside. you have got to give us the schematics of your final product.
  3. I will. In fact, if successful, I'll post the entire circuit diagram here.
  4. A9X


    Dec 27, 2003
    Sinny, Oztraya
    What have you ordered? Are you wanting to base your designs on that or can you source other parts. DS have quite a limited range of stuff.
    Not quite sure what you mean by this. Could you elaborate? Do you want gain (how much?) or buffering only, mixing pickups before the preamp or individual inputs, what sort of battery life do you want? etc... You mentioned no EQ. Do you want opamps or discrete components?
    There's nothing much in them, and most sound awful.
    Built a few now, most were at least OK, and better than the generic MM card I got with some pups I bought. The discrete ones I have in my Alembic are great but a dog to build (matching 2SK369's is hard work), they need a decent size cavity and absolutely eat batteries.

    Also remember when you A/B to normalise the levels as close as possible. I've done lots of audio testing over the years and without fail, people will prefer the louder one, even if the level is only slightly different.
  5. IT's finished!!! :)

    I ordered all my parts from Dick Smith. It was a really simple design using just one TL071 opamp.

    I made it primarily to get a little more gain out of my pups without colouring the sound or affecting the controls. I think I've been successful.

    I have it set up with a trimpot to adjust the gain and then I let the volume and tone knobs already on the bass do the work. In other words, the preamp is the last thing in the chain on the bass before the jack.

    I know what you're talking about by "normalising" the signal. The least amount of gain I can get out of this (based on my design) is 3db...even here, there is a noticable increase in signal...but you see...besides providing a buffer to the cable (which can be a good thing), that's exactly why I built her...

    I've tested it on my Yamaha RBX170 PJ bass...and I must say that the bass sounds slightly better in P-bass mode (more open) passive. But when I put it on the J-pup (which was a little anaemic sounding) it now kicks slap-poppin' BOOTY!!! :hyper:

    I currently only have it set up as an outboard unit for testing, but when I make up the inboard version. I'm going to definitely put a bypass switch (probably via a push-pull pot)...or maybe a toggle switch (haven't decided).

    When I tried this on my wishbass, which has a KA soapbar in parallel...I got the same tones as before with just a little more volume...again, this is useful and will probably eventually adapt this test model for this bass...

    Some other tests I'm going to do, include hooking up 18V instead of 9V (the TL071's can handle this no-problem).

    What do these things cost me in parts??? <$15 AU per preamp...now THAT'S a bargain...and they're not that tough to assemble either.

    are they quiet? You bet they are!

    just have to watch the gain...too much and they distort (happens with most JFET Opamp designs) hence the 18V test...I currently have it set to around 6db and that is plenty.

    anyway...that's enough for now...I'm satisfied :) :)

    I'll try and get some sound clips together soon.