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What's up with my preamp?

Discussion in 'Pickups & Electronics [BG]' started by Wademeister63, Apr 6, 2005.

  1. Wademeister63


    Aug 30, 2004
    Denton Tx
    I built a bass and it sounds great! Has a Bart NTBT preamp that I don't really get along with though. The volume knob only needs to turn about 10 degrees from off to full volume. In other words, it's acting more like an on/off switch than a real control. I tried a couple different pots in place of the volume pot that came with the preamp, but it all came out the same. I think I tried a 250K and a 1M ohm for my experiment. I played around with the gain trimpot but it seemed to make no difference in the volume pot behavior. The trimpot was turned all the way clockwise when I got it, and I ended up leaving it there. That leads me to the next question.

    The volume difference between active and passive is enormous. Active, I have to turn my preamp input way down or it distorts, but in passive mode I need to crank it up to hear it. Can I turn down the trimmer to even it out a bit? My attempts at messing with the trimpot didn't seem very effective, but maybe I was a little timid about my adjustments at the time.

    Also the thing gets hissy if I turn the treble up much above the center notch. I've heard the same from some other people. Is that just normal for this preamp?

    I'm getting ready to build another bass and I'm planning on using the Bart pickups. I love the tone I have in the first bass, but hate the preamp quirks. Any advice on what preamp I might look at that will help me avoid the present problems I'm having?
    I'm building mostly from maple with an ebony fretboard, so I'm expecting this to be a very bright bass. I'm hoping the preamp treble will normally be rolled off to tame the beast a bit, and if the preamp has some color of its own, I'd like it to be warm and fat.
  2. luknfur


    Jan 14, 2004

    I've had the NTBT and had no problems. Any treble control for the most part will result in more noise when elevated but it's the Aguilar pre's I had taht were more inclined to create noise in that situation. The Bart was never a problem till about 3/4 - maxed. Obviously - varibles such are pot values, brighter pups, etc. have an impact. The trim pot can be used to reduce gain where distortion exists but if it's set between 1/2 and 3/4 or less, I doubt that's the problem.

    Probably more Bart pres installed in boutique basses than the rest combined so that reflects quality. But I've found EMGs, Bart, Aggie pres to be more alike than different - they're all good for what they do and I have found one to be not better than the other. The differences are primarily subtle (Barts have a trim pot, Aggies don't - etc.)

    I'm guessing incorrect wiring/pots/grounding. Volumes should be audio and stick to recommended values in general. There are Bart diagrams and I would go by those exactly cause you know if there's a problem, it's not a result of the wiring scheme and that eliminates one variable in trouble shooting. Once it's working correctly, then it can be jacked with.

    There is something in particular that causes the volume cranking you alluded to but don't recall what it is off hand - a search should locate it as it's been addressed many times in the past. I'd double check for correct wiring cause obviously the sweep gradation is being skippped.