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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.
Post Subject: Neutral ground path in humPosted by drdna on: 2/21/2009
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 Romy the Cat wrote:
You will have a noise if you have more than one references to ground. You can easy test it by lifting ground from PP2000 input. It would not be a good way to operate but as the hum-test it will do.
Yes, I tried this, lifting the 3rd prong ground from the PP2000 plug changes some hum, but it does not make the hum go away. I also lifted the ground from each device in the stereo, plugging them in one ata time. This also had no effect on the higher pitched hum.

 Romy the Cat wrote:
I still do not see how it might be PP2000 related and I have no idea why you lifting the PP2000 output still, as you report, it has the hum. It just does not makes since to me.
No, when the PP2000 is totally unplugged from the wall (and hence the neutral path which is also grounded is removed), the hum disappears. Then the whole stereo is functioning like some giant battery operated device.

This is odd, since it seems to be the AC mains connection that is leading to hum. There is only one path to ground at that point, the neutral path through the AC plug. Is it possible that there is a ground loop problem within the PP2000 creating the hum, which is eliminated when there is no external reference to ground? Or what do you suggest?

Adrian

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