M-80 + FOH = Unhappy amp

Vic Winters · #1 01-30-2009, 02:40 PM

A few weeks ago I played a gig at one of the regular joints I play. They finally got in house sound instead of expecting the bands to bring their own sound. To make a long story short, I run his XLR to my MXR M-80 and turn on my amp, and get nothing but that horrible buzzing you get when you ground the tip of the jack with your finger. No signal from the instrument at all. Ground lift switch did nothing to rectify the situation. Unplugged his XLR, no awful buzzing from my amp. I switched to my backup Whirlwind IMP-2 and played with that for the rest of the night with no buzz. A few weeks later I played a different bar with my M-80 and had no issue. I've also played the original place with different sound and had no issues either. I have to play the original place again in a week and I'd prefer to use my M-80, is there anything I can do to prevent the same thing from happening?

runmikeyrun · #2 01-30-2009, 03:42 PM

phantom power maybe? I dunno.

stflbn · #3 01-30-2009, 03:46 PM

If the rig is working other places it pretty much isolates it to something coming from the board.

JohnDavisNYC · #4 01-30-2009, 03:49 PM

are you running the M80 off of phantom power, battery, or a powersupply in your board? could be some weird grounding issue between the power at FOH and the stage power?

i would try running it off phantom only and disconnecting any power supply cables... or ground lifting your rig?

sounds like something is messed up at the club.

john

Vic Winters · #5 01-30-2009, 04:24 PM

I run power from a 1-Spot. Ground lift on the pedal did nothing. No ground lift on amp except for DI which I don't use.

irvinz · #6 01-30-2009, 05:29 PM

i think you might have phantom power from the board running through, that interfering with the 1 spot? i recall my m80 not liking phantom power unless it was run solo and still using the parallel output to an amp as well.

Alaska Bass · #7 01-31-2009, 01:27 AM

If he had a damaged cable it could cause some issues. Keep a spare cable or even better, bring your own DI with a 1/4" in, 1/4" out and XLR out. This allows you to keep your signal fairly direct to your amp while giving a clean signal to FOH.

As for the phantom power, it can definitely be an issue. Unfortunately, in that type of place the board is probably pretty cheap and only has a phantom power switch that powers multiple channels (good boards have individual switches on every channel). If that is the case, FOH may not be able to shut it off if they are running condensor mic's on a neighboring channel.