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Oh. That's what's wrong with my amp.

Discussion in 'Amps and Cabs [BG]' started by barthanatos, Apr 9, 2006.

  1. barthanatos

    barthanatos Insert witty comment here

    Feb 8, 2006
    South Carolina
    So I've got this SVT-2 Pro that I picked up at BassNW. I was told when I bought it that it had been serviced by an Ampeg certified tech to factory conditions, and had all new tubes. Good deal. Great amp.

    I played it for awhile, and decided to fill up the rack case that has holding my amplifier, 'cause I just couldn't have four empty slots there, y'know? So I add some things, including a noise eliminator and a compressor. I hook it all up, and hey, everything works. Sweet.

    After a while I notice that the amp is pretty quiet. I'm thinking maybe I didn't let it warm up enough, or I overdrove the tubes a bit too much, or something. I'm not sure. I notice that when I send a line out the the sound board that I'm only giving a very (not useable) weak signal to the sound guy. I fiddle a little and discover that when I put the Pre/Post switch in Pre, sound guy gets a good signal. Huh.

    I also notice that if I turn up the gain knob on the compressor, that the speaker makes a god-awful noise that is scary and sounds like something is going to break if I let it keep going. Very peculiar.

    For some reason (this is after a couple weeks) I decide to unplug all the effects from the effects loop. Amp is immediately loud as hell. I'm happy, of course, but a little confused. I decide I have a ground on my effects loop. Not a 0 ohm ground, but a ground. I decided to try and figure out where in the signal chain the ground was, and do a bit of plug-and-chugging with the wires.

    I hook up a cord straight from the send to the return. Good volume.
    I hook cords up to put the compressor in the signal chain. Virtually no sound comes out whatsoever. I hit the "bypass" switch on the compressor. Tons of volume. Hmm.
    I check the noise eliminator in the fx loop by itself. Very weak sound, but more than from the compressor. I hit the bypass button. Lots of volume. That sucks. I was really hoping it was just one component that was bad. How could they both be bad? Not likely.

    At this point (today) I ask myself, "Self ('cause that's what I call myself when I'm talking to me), surely the send/return points aren't backwards. Surely." So on this whim, I try switching the send/return cables, with trepidation, half-expecting to blow something up.

    Sure enough... the send/return jacks on the effects loop of my amplifier were backwards. The jack labeled return is actually hooked up to the "send" signal path, and vice-versa. Hallelujah, problem solved. Everything acts totally normal now. I am so happy.
  2. anderbass


    Dec 20, 2005
    Phoenix. Az.
    Good job locating the problem.
    I have a Joe Meek mic preamp, that came factory equiped with a reverce wired f/x send jack.

    If you were dyslexic, you never would have noticed, those two jacks were reverced......;)

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