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Amp Ground Plug - Safe to Remove?

I've just purchased a new Arcam system, including a two-channel power amp for my rear speakers. Straight away, I got a bad humming noise through the rear speakers. I tried swapping ICs, moving things around, disconnecting the tv cable etc but nothing fixed it.

I live in Australia and the power cord for the amp has a three prong plug, one of which being the ground. I've removed the ground plug using a pair of pliers and voila, the hum has gone. My question is, is this a safe thing to do? The idea of touching the power button and receiving 230 volts is not too appealing.

If it's not a good idea, is there anything else I should try? It only the rear speakers and the Arcam amp that are affected. I use monoblocks on the front three channels and they have no problem.
baileyincanberra
5 responses Add your response
ghostrider45
449 posts
 
You're probably OK, but to be sure take an AC voltmeter, attach one lead to ground, and probe each chassis with the other. If you see more than about 5 volts or so then you have a problem.

Modern gear runs the power leads (hot and cold) directly to the power transformer (perhaps through the power switch). Unless there is leakage to the chassis all will be well.
joeylawn36111
574 posts
 
I agree with Ghostrider. I was about to post to say it was probably OK, but I did'nt think about the AC Voltmeter test. Great idea, Ghost. Voltmeter test will prevent possible electrocution.
baileyincanberra OP
34 posts
 
Thanks for the responses. I'll definitely get a voltmeter and check it out, though I gather the risk of electrocution is pretty small. One other small question - when you say 'attach one lead to ground' where specifically should I attach it (forgive my ignorance)?
gs5556
1,235 posts
 
The purpose of the ground plug is to return a fault current, such as a live wire touching the equipment chassis within, back to the panel. This does two things: it reduces the chance of shock or worse, and it enables the circuit breaker to trip - possibly preventing a fire. Whether you disable it to get rid of a ground loop is your choice. But there is a potential danger present, just like not wearing seatbelts - no problem as long as you don't hit a tree.
ghostrider45
449 posts
 
Connect one voltmeter probe to the ground plug in your wall outlet and probe the chassis with the other.

Gs5556 is correct, there is some future risk if leakage chassis leakage develops.

However, if the power amp is connected to the processor (or preamp) via a shielded cable with the shield connected at both ends, and the processor or preamp is connected to the AC with a grounded power cord, then the power amp is effectively grounded via the shield and there is no risk at all. The shield effectively ties the power amp chassis ground to power system ground via the processor/preamp.
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