Ground domain separation

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I'm looking for the best way to split (or connect) the chassis and signal ground in my CD player. I belive I'm looking for a choke that can do the job.

Any tips or references to older threads are welcome!

One of the problems is that I can't know if the CD player will be connected to mains earth. In Europe you typically use 2-prong mains without safety earth, while in the US 3-prong equipment is common. Also, I can't know if the amp connected to the CD player will have its signal ground connected to mains earth or not. So there is the potential of ground loops on one side, and on the other side there is the danger of complete isolation from earth.

What I have done is to make a complete signal ground domain inside my box that connects to the rectifiers and through those to the secondaries of my transformers. Around this there is an aluminium housing which may or may not be connected to earth. There is a teeny bit of unavoidable 50/60 and 100/120 Hz stray capacitance between the transformer/PSU and the casing. But all in all there seems to be a good galvanic separation between mains and chassis.

I want the player to be safe to use and good sounding (no hum) regardless of the earth configuration and regardless of whether I use phono cables or XLR to connect to the amp. And I hope there is a single component I can use between the ground domains of my player to achieve this.

So what I guess I need is a choke with high impedance at 50/60Hz to prevent hum and low impedance at DC to prevent charge buildup and shocking the user. You should be able to hold the chassis of my player in one hand and the amp or water pipe or stove or whatever in the other!

Also, I've been told that the screen of the XLR cable should be connected to the chassis rather than to signal ground. That is to lead any current due to ground loops away from flowing in my signal ground leads.

Any opinions on that?

What it implies is that the choke between chassis and signal ground will also be in series between XLR screen and signal ground.


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