Bizarre Buzz

ccscanlon

Hi, I have a new (to me) Adcom GFA-2535 amp connected to my rti 5.1 speaker setup. I'm using my Onkyo 705 as a preamp. I've never had any noise issues until I hooked up the new amp. I've troubleshooted it by disconnecting and unplugging everything and leaving the amp plugged in and the speakers hooked up and it still buzzes. I've tried other circuits in the house and it still buzzes. The strange thing is that the buzz is only audible close up if the amp is connected to the receiver but gets much louder when disconnected. The buzz level is constant and doesn't go up and down with the volume. I don't have cable. It could be a defective unit but before I try to return it or buy any kind of power filter (which I can always return if it doesn't work) I thought I'd see if any of the nice people here had any input or recommendations on ways to fix it. Thanks!

TNRabbit

Do you have ANY slider or rotating knob dimmer/variable fan switches in your house? They are NOTORIOUS for causing this type of interference...check any fluorescent lights as well.

ccscanlon

Thanks TNRabbit, I don't have dimmers but my fan is variable speed with a dimmer but that is all controled with a remote and the switch is in the "off" position on the wall. I wonder if that would still affect it. Also I have a couple of fluorescents but those are also almost always off.

unc2701

Is the buzz coming from the speakers or from inside the amp?

Inside the amp:
google: DC toroidal hum. There's a simple circuit to fix this or you can buy a humbuster:
http://www.psaudio.com/ps/products/description/humbuster-iii?cat=accessories

From the speakers:
Probably ground loop. Run a piece of wire touching bare metal on the chassis of the onkyo to the chassis of the Adcom. If the hum goes down, it's ground loop. There are a few solutions and not every one works in each situation.

Let us know what you find.