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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
podeschi's avatar
podeschi
301 posts
 
great thread, commenting here so it is parked in my threads.
grimace OP
624 posts
 
The plot thickens. I took the amp to a local tech who a) could not duplicate the hum and b) could not find anything wrong with the amp - although he did say it sounded very nice. Not quite believing it, I went and listened for myself, and he was right.

So, since that is now two places - Cary and my local guy - who've been unable to duplicate the hum, I guess that points to something in my AC system causing the problem.

So now what? Dedicated line? turning off the fridge is not an option.
grimace OP
624 posts
 
In addition, I figured out which circuit the hi-fi is on, turned everything else in the house off, as well as unplugging everything else in the room, and the amp still hummed.

I also used a ground tester and the outlets were showing that they were in fact grounded.

grrrr.
lifeengineer
55 posts
 
Why not try a PS audio humbuster ?
jea48
2,944 posts
 
Grimace,

When you sent the amp to Cary did you also send along the power cord that is used on the amp?

How about the repair shop. Did you take the power cord with the amp?
>>>>>>>>>>>

I assume you have a multimeter.

(1) With the amp turned on measure the AC voltage at the wall duplex receptacle.

(2) With nothing plugged into the duplex receptacle measure the AC voltage.

(3) Check the AC voltage from the hot contact to the equipment ground contact.

(4) Check for AC voltage from the neutral contact to the equipment ground contact...
Make sure the meter is set to AC auto.
Make sure both meter test probes are making good contact.

Post back the measurements.
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