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EHX bass micro synth fuzzing out

Discussion in 'Effects [BG]' started by Pbassred, Dec 2, 2013.

  1. Hi, I just bought a used unit. 24V PSU (original) In a wooden box. It also has a CE mark. That probably dates it to after 1993. I’m playing an Active YamahaTRB5 through it. No matter what I do. I can’t get a clean sound through it at any meaningful signal level. My bass is active but not very hot output. The adjustment screw underneath can’t do it. Even switching the effect off with the foot switch doesn’t cure it. There is a background buzz. I’m running into a mixer. The clip light never flashes so its not output level.

    I’ve studied the Ed Friedland Youtube and I can’t get clean effects when I copy his settings.

    I would say it was maladjusted but I can’t see any tell-tail damage to the screw heads (its what we look for where I work).

    Looking at the schematic, (Sht 1) there is an input followed by an op amp (these don't usually degrade - only die.). The signal then goes to the bypass switch on page 3 or continues through caps to another opamp. Since the distortion happens whether its bypassed or not. The fault must be here - probably the caps. ...... Unless I'm wrong.

    EXH microbass synth 1996.pdf

    Is this common in older units. Any advice?
  2. Lownote38


    Aug 8, 2013
    Nashville, TN
    They aren't true bypass, so if it's making noise, it will do so even when it's off. If it is making noise when it's on and off, something is wrong with it. I've owned two of those (the original and the reissue) and neither one ever did what you're describing. At the very most, it colors your tone a bit when it's off, but otherwise shouldn't make any extra noise. I just invested in the new smaller version, and that was the way to go. True bypass, but all of the same features as the original.
  3. No it isn't true bypass, but the only bit that is active, is the first gain preamp. If the switch is pressed, the preamp signal goes straight to the output jack. If the output is dirty, the preamp is dirty. ;)
    I'll do the true bypass mod when its fixed.
  4. shenanigans


    Sep 9, 2013
    There is a second trimmer in the pedal. My memory says one adjusts the gate and the other adjusts input gain. I can't 100% tell if you ruled those both out from earlier posts. I don't see the gate trimmer on your drawing.
  5. I did some reading arround and found conversations about adjusting the "squelch" pot. This rings true with me. In the early 80s CB radio days, the squelch knob was a way of shutting off background hiss - essentially, a gate.