A bit OT: effects loop hum

[jayp5150]

I just noticed after replacing the 12VAC adaptor on my Digitech RP-series reverberator that I have a horrible hum if plugged through the effect loop of my 5150.  If I plug direct (up front) it does not do it as much, but the reverb sucks then.  I plugged a single cord from the in to the out of the loop, and no hum.

Could this be something in the power supply.  The only 12VAC 500ma I could find around here quickly was at Radio Shack.  It's a multi-selectable-voltage one for an answering machine.  The voltage and amperage matched, though.   Isn't that all that matters?

I did change the plug to the one from the original pwr supply, so it's not a bad connection.

Any clues where to go now?

Thanks ahead of time.

[niftydog]

if it is 12VAC output then the power supply isn't the problem.

I'm willing to bet it's a ground loop. Did it hum with the old supply?

It's a multi-selectable-voltage one for an answering machine.

hang on... it's kinda unusual to have a multi-selectable output wall wart with an AC output... are you sure you haven't mixed up AC and DC wall warts?

[jayp5150]

I just double-checked, and it is AC.  It's 800ma, though, not 500 (the original was 500).  Shouldn't be a big deal, right?

It may have hummed a bit before, but not like this.  I'll try it in another room, or with a ground lift.  I didn't think of that before.

Thanks.

[niftydog]

cool. Just lift the ground on the lead from the effects loop to the digitech.