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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 3 responses by jsteigert

jsteigert OP
14 posts
 
Ed, Both pieces are true balanced designs. I am not clear why Plinius lays out their spec in the way that they do. I need to ask them.

Sean, Since the ground at the panel is common to all circuits, I am not surprised to find out that dedicated lines won't help. I think you are right - I need to determine whether there is a basic mismatch between Pass and Plinius. So a call to Pass is also in order. The good news is that both companies are very responsive.

Gs5556, I think it it interesting that the Plinius open ground switch achieves isolation that floating the power cord ground does not. Any thoughts on this?
jsteigert OP
14 posts
 
Sean, If you look inside the Plinius it has two HUGE toroids separated by a metal horizontal divider from the compartment containing the circuit boards. This is already beginning to look like a pair of Faraday cages to me. J.
jsteigert OP
14 posts
 
Mystery solved. I was working with a dealer on these speakers when this event occurred, getting ready to bring them home. He was behind the amp operating the switch. It turns out that things were actually working as they should have. The big hum came when he switched the amp into OPEN mode and went away when he switched to chassis ground, exactly as SHOULD have happened. The only thing backward here was the communication between us. Thank God for little things.
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