Originally Posted By: Dignan
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Everything is wired correctly. A standard cable with RCA connectors goes from the subwoofer preout on the receiver (a Denon AVR-S510BT) to the left channel input on the amp. The amp is set to bridge mode with power set to "on" for testing purposes. The speaker is wired to the left positive and right positive as per the manufacturer's bridging instructions.

The result: a buzz. I'm getting a significant buzz from the sub. If I turn the amp's volume up to max, it's extremely noticeable. All the way down to around 10% it's pretty clearly audible. The buzz volume changes with the amp's volume, not the receiver.

I tried another source on the amp and didn't get this buzz. It's only from the receiver, whether the receiver is on or off. When the receiver is on, I can tell there's audio underneath the buzzing, and when I played a youtube clip with substantial bass, I definitely heard it. So much so that I'm even more frustrated that this buzz is there because I'm excited about how good the bass sounded.

... a ground loop. They suggested I try plugging the amp into a different circuit than the receiver. I tried that tonight and it didn't have an effect. Should I even bother ordering a ground loop isolator?
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’Ground loops’ (and grounding issues in general) can be tricky to diagnose.

Does the amplifier have a two or three pin power plug into the wall AC?

Is the subwoofer itself grounded?

Have you tried non bi-amped mode on the sub amplifier?

Have you tried connecting everything (everything including all things plugged into the other receiver inputs) to the same power bar, into a single AC outlet?

Disconnect as much stuff as possible from the receiver. Minimal or no input connections - Play an FM radio for sub-woofer testing