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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.

Post Subject: Ground noisePosted by PurePower on: 3/22/2010

To hear hum in the speakers usually requires a combination of conditions - including sensitive speakers and a ground system capapble of carrying the noise signal.

I would place my bet on common mode noise being carried on the safety ground long before blaming RF. Every time we have investigated this kind of issue it has been very clear on the scope - the noise is visible on the oscilloscope when you probe the neutral to ground pair, but the AC will have a clean, noise free sine wave.

Ideally, a perfect ground system will have no potential between neutral and ground - and thus no capacity to carry a noise signal. That's why two systems can be identical - yet one has hum and the other does not. No two ground situations are identical.

I have to admit that creating a perfect ground is not always an easy task - but we have been very successful in removing ground noise by finding and correcting ground problems. It is definately the first place to look.

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