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Ground Cheater plug or....

Maybe this isn't a good idea, but I thought I'd ask anyway.

I have what I believe to be a persistent ground loop hum from my amplifier. It's quiet, inaudible if music playing or unless you're standing next to the speaker, but knowing it's there is annoying.

I've heard suggestions to use a cheater plug to defeat the ground, but it seems counterintuitive to stick a 35cent plastic plug between expensive cables and power supplies. My question is, couldn't you accomplish the same thing by disconnecting the ground wire in the outlet, and still exact the benefits of better cables?

I'm sure the fire marshall would disapprove, but I'd like to hear what the hi-fi nuts have to say.

Cheers!
grimace
puerto
372 posts
 
I use cheaters on my mono blocks to solve the same issues - nothing else worked!
broimp
10 posts
 
I had the same problem. Cause was the fact that one of my amps uses a grounded plug, the other not and they live on the same circuit, unfortunately. You may want to look to see if you have a similar situation. Two and 3 prong devices on the same circuit can cause this problem. Start disconnecting and reconnecting stuff and you will probably find out what is doing it. Chances are nothing is broken. I wound up using a cheater. No fires so far (10 years)
broimp
10 posts
 
Yes all devices you have are grounded, some are chassis grounds (2 prong devices) and some externally(3 prong). The problem is that these grounds are just different enough to create a small current flow when they are on the same circuit and that is what you hear as 60 Hz hum. Rewiring all to be 3 prong will most likely fix, but that is pretty extreme. Not saying this is your issue, just that it was mine.
grimace OP
624 posts
 
So here's what fixed it. I switched pre-amps, and suddenly the amp was quiet, but when I turned on the pre-amp the hum came back. It had mysteriously jumped between components! To finally get it to settle down, I stuck a cheater plug between the pre-amp and the power supply - the PS is still grounded at the wall - and that fixed it. I don't hear any sonic degradation from the cheater. Cheaters seem to be controversial, but at this point, and since the PS is still grounded, I'm not arguing. But hell's bells. it took a year to figure out.
almarg's avatar
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almarg
9,670 posts
 
Did you ever try shorting the amp's inputs, as I had suggested? Doing that would probably have led to the conclusion (which now appears to have been the case) that the hum that was heard while nothing was connected to the amp's inputs did not have the same cause as the hum that was heard while the preamp was connected. Knowing that would probably have led to a much quicker resolution. See my post dated 3-30-12.

Regarding the safety aspects of using a cheater, IMO it's your call. While the risk is very small, assuming that the equipment is in good condition, it can't be said that the risk is zero. And if that very small risk were to materialize the consequences could be very serious.

Regards,
-- Al
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