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.