Discussion on grounding

This will be my first of many questions about grounding, one of the most confusing topics I have to deal with in DIY.

RCA inputs each have their own signal ground and so does each section of a dual gang potentiometer. Intuitively I would use 4 wires from the RCA jacks to the pot and then wire each signal ground with the respective channel getting attenuated. However in my observations I see a lot of people link the RCA grounds and use 3 wires to the potentiometer, which also has linked grounds. Is using 4 wires considered bad practice? If not is there a difference in circuit behavior or is the other ground wire considered redundant?

Edit:

Found some links to PCBs that support both lines of thinking. Here is one from AMB audio that uses one big ground plane.

http://www.amb.org/audio/epsilon27/

Here is one that preserves the grounds for each channel.

http://www.pavouk.org/hw/pot/en_index.html

 

I am interested in this as well; there's a lot of info out there about the why's but a lot less about the how's.

 

The right way to do it is a wire from each RCA ground to the circuit star ground, and a wire from each pot ground to the circuit star ground. Connecting the 2 RCA grounds together and then connecting that to the star (and the same for the pot) is fine. Running from the RCA to the pot and then to ground is more likely to pick up noise. And a ground plane is effectively a large star ground.

You might start here: http://www.diyaudio.com/forums/diya...udio-component-grounding-interconnection.html

 

That is one epic article! I'm going to need awhile to read this...

 

I've linked this a few times, but I'll link it again, because it's one of those wonderful articles that you can still learn from on the third or eigth read. There's a short section on how to connect volume pots.

The G Word, or How to Get Your Audio off the Ground

Here's the short of it for volume pots.



The problem arises when the Out- of the first amp, the "ground" of the pot, and the In- of the second amp are all connected to different grounds, because each one is a signal reference. And pots are tricky, because they have a single signal reference for both the input and output.

I've had good luck connecting the pot directly to the differential input of its stage.

In a single ended stage, ground is the signal reference is In-. That's the ground that your pot should connect to. If the In+ of a common cathode amplifier is its grid, the In- is at the bottom of its cathode resistor.

This article touches on how to manipulate the signal reference of single ended tube stages to some very neat ends.

 

dsavitsk's answer is what you want.

Minor addition though: a ground plane is only like a star ground if the plane is large enough to make any current flow from components negligible (it usually is), or the components are placed or the plane is routed such that the current flow from one won't interfere with the other. But don't assume a small ground plane is good enough just because it's a "relatively large-ish square on your PCB".

 

I think the one possible caveat to this is if you are using braided rather than shielded input wiring for noise rejection - then you really need a nice three wire (l, r, g) braid, not a twist, running from isolated rca's to the pot, with pot ground running back to the star.

This is how I ended up wiring my wire se se after wading through some massive threads on diyaudio, and it runs dead quiet, notwithstanding that many folks seem to have trouble in this regard with their wire builds and/or with noise once they connect safety earth to the star. (Photo here: http://www.diyaudio.com/forums/head...headphone-amplifier-pcbs-253.html#post4753326 )

 

How exactly does grounding work for devices that use a two pronged wall wart? Examples are the O2 and the Magni/Modi/Mani devices by Schiit. Does everything just float in the chassis?