Originally Posted By: tfabris
I'm assuming these were opto-isolators?

I used this. I admit to having no idea if that was a good idea or not. I just used the black connectors. I was unclear about which direction to hook it up, so I tried both ways.

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Can you describe this in more detail? What exactly do you mean by "tried another source on the amp"?

I simply attached the only playback device I had handy, a Chromecast audio. Naturally, music sounded like crap through the speaker but I didn't get the buzz at all.

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While we're here, how is the receiver output wired to the subwoofer amp input?

Simple cable with RCA connectors on each end. All I had lying around was a composite cable that I just peeled one wire off of. This has worked for me in the past. Clearly not a great cable but it should work, no?

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Also, how sure are you of the ohms of the subwoofer, since the sub amp probably requires different wiring for 4ohms or 8ohms.

Pretty sure it's 8ohm. It's no world-beater, but I just needed something basic. The only wiring difference on the amp is that I believe I couldn't bridge a 4ohm load, so yeah that would probably have problems, but I tried wiring as a single channel load anyway and had the same result.



Originally Posted By: K447
Apple TV and Tivo would also bring the TV into the equation. Everything in a connection chain can cause or link ground loop noise.

Good point. I'll check the TV plug polarity since I'm sure that one isn't grounded either. Maybe a different power strip? Would a backup battery help mitigate this?

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If the ground loop isolator has a spec for frequency response, it may roll off into the lower Hz range. It may also have an insertion loss dB spec, perhaps even a frequency chart.

I didn't think about frequency range of the isolator, I'll admit. And the Amazon listing doesn't mention it...and it didn't come with any documentation.

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Generally speaking, connecting portions of the linked equipment to other/distant ground points won’t fix ground loops. Often make it worse.

Electricity always travels in a loop, including induced ‘noise’ current from ground point voltage differentials. The key is to find where the different ground point voltage potentials are located and somehow break the circuit loop through your equipment.

This...is very frustrating...

Perhaps I need to find a receiver with a built in sub amp? Does such a thing exist?
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Matt