Chassis ground and balanced mode - please help me


Plinius SA 102 has a ground switch (open vs. chassis) that they specify should be set to Chassis when running in balanced mode.

1. I assume that this has to do with achieving proper noise cancellation - but if not can someone straighten me out?

The problem: I am trying to run the Plinius with a Pass Labs X1 pre in balanced mode. There is a LOUD ground loop hum when ground is set to chassis that goes away in open position. Floating one of them does not help.

2. If I power the Plinius and the Pass using two separate lines back to my panel, will this ground loop problem be removed?

3. Will I be able to solve this problem?
jsteigert

Showing 4 responses by sean

I would suggest calling Pass Labs up and see what they have to say. Other than that, running dedicated lines for each component would not correct the problem if there was a difference in ground potential between the lines. Since you've floated the grounds on both / either component, it does not appear that it is an Earth ground based problem but is simply a conflict in impedances / loading between components. Sean
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J: While i don't know how common it is in audio gear, some RF designs make use of two different "grounds". One is a board ground and the other is a chassis ground. In some instances, it is beneficial to have these two grounds separated and in some instances, it works better to have them tied together. I don't know if this is what Plinius is doing with their switch, but it might explain some things.

Personally, i've always wondered why audio components tied circuit ground to chassis ground ??? If audio engineers were "smart" ( some really are, some ... ), they would use the chassis as a "Faraday cage". In effect, the chassis would be tied to electrical ground but NOT to circuit ground. This would increase the rejection of RFI and minimize the potential for damage via inducing stray voltage ( static shocks ) into the circuitry. While this would mean that all of the external signal connections ( RCA's, XLR jacks, etc.. ) would have to be isolated from the chassis electrically, that is not really a big deal. It might raise the cost of a product slightly, but hell, we're already paying too much as it is yet we come back for more with every purchase. Sean
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J: I think that a phone call to both manufacturers might offer you quite a bit of info. I'd be curious as to what you find out, so please, share the wealth once it falls into your lap : ) Sean
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PS... I was not talking about Pass or Plinius gear in specific, but all audio gear in general.
hahaha.... as they say, it's the simple stuff that'll kill ya : ) Glad to see that it really was simple : ) Sean
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