Question on behalf of our synth player

[justinhedrick]

the synth player in our band recently sold his line 6 M13 pedal and desided to go towards a dedicated stomp box format. so, he got a Crowther Hot Cake, and 2 of those new Eventide boxes (modulation and delay).

he has a Moog anniversary addition (the big on with the digital screen in the middle and an old Juno (i think). he is running each of those stereo channels into a mackie mixer (6 or 8 channels, i think) and then running the effects off the aux sends. the first day he did this he was recording in chicago with his improv noise/jazz outfit and said there was ZERO noise (he was running straight out of his board, no amp). at practice last night he was running into his keyboard amp, plugged into the same outlet and it sounded like the effects were noisy as hell. originally he thought it was just the hotcake (which is on it's on aux), so he unplugged it. still noisy. is sounded like even with the effects in bypass it was oscilating. we tried different cables, different effects orders, plugging everything in one chain in a single aux sent (like a guitar setup).

any thoughts?

[bass sic]

He can stop the synth nonsense and pick up a guitar.

[RacerX]

plugged into the same outlet and it sounded like the effects were noisy as hell

Ground loop.

[justinhedrick]

Ground loop.

would he aleviate this by plugging into different outlets?

[RacerX]

That will likely do the trick. If not, there are other ways around it. Try that first before you start looking at ground loop lifters and such.

A power conditioner is another good idea if he has lotsa shit to plug in. Voltage variations can play hob with complex setups.

Read this:

http://www.epanorama.net/documents/groundloop/problem_solving.html

[LogicalFrank]

Actually, plugging into a different outlets is more likely to create a ground loop. My guess would be power supplies though. Have you tried plugging straight into the amp, different amps, etc?

[Lumpy]

Some pedals sound horrible when the battery is low (if he is running on batteries). Also, if he boosted the volume on his pedals, anywhere on the mixer, or synth output, in order to compensate for a weaker amp (or lower amp volume, or louder band), that can result in some background noise, in certain circumstances. (the 'gain structure' of his signal chain). Try making volume adjustments (down) along the line, and see if that makes a difference.

[Hemisaurus]

My suggestion would be to go at it systematically, I'm guessing if it's in your practice space you have time. Treat it like an amp repair and work logically from the output backwards.

First off set it up like it normally is.
Grab a pair of headphones and stick them into the mixer headphones jack, is there a buzzing there?
Unplug it from the keyboard amp, is there still a buzzing?
Unplug completely (both input and output jacks) each effect in turn, did unplugging one of them cure it?
If no one effect being removed cured it, remove all of them, still buzzing?
Unplug the synth(s) from the mixer, one at a time if multiples, did one being unplugged cure it?
Unplug all the synths (and effects still unplugged) is it still buzzing?

If a particular effect or synth is causing the buzzing, look at how it's being powered, is it grounded to earth ground, or does it use a wall wart (little black power supply?) Sometime reversing them can help, but the problem is often that they cause the ground to float on what they are powering, if you use multiple warts, you have multiple ground levels.

I've run common grounds through an effects rack, never tried it with a stompbox chain. There are all kinds of issues, if the exact same setup works elsewhere, maybe it's the practice space? Could be your power is bad, or maybe your near a radio tower? One of our old guitarists, his wah would pick up radio and be horribly noisy in his practice space, but nowhere else, we figured there must be a transmitter near his house. Fluorescent lights another great source of noise, dimmer switches as well.

Not going to go into much more detail, the rest of what everyone else says applies, power conditioners may help, checking your gain staging may help, etc.

Good Luck

[Lumpy]

(Oops, I said gain structure, but I should have said gain stages.)  the signal may be too hot, somewhere in the chain.

[Hemisaurus]

Err I don't know which is correct structure or stages, I was just mis-remembering what you typed.

Distortion is a more likely product of too hot a signal, too quiet a signal gives you more hum, as you are amplifying the noise floor along with the signal. There's a saying that I can't bloody remember right now, fill it in someone, please 

[RacerX]

One if by land; two if by sea?

Righty-Tighty; Lefty-Loosey?

If it moves, shoot it; if it doesn't, paint it OD Green?

[Hemisaurus]

No something about making a signal hot enough to beat the noise floor, but not so hot as to clip, kind of like garbage in, garbage out, but not. I'm buggered if I can remember what it is. Maybe I should google 'studio pearls of wisdom'

[RacerX]

Gain in; More Gain out?