Grounding and safe procedures for steel and wood case for amps

[zintolo]

Hi,
I've always used steel chassis for both guitar, bass and hi-fi amps, where one earth connection and one ground are enough.
This time I want to build two mono and two stereo amps with:

1. a steel plate on top;
2. a steel plate on the back for RCA input, power socket and speaker outputs;
3. wooden sides.

What are general suggestions to ground them?
Thanks in advance for your help.

Roberto

 

[rkoonce]

I would securely connect a wire to the top plate and connect it to the rear plate where the mains ground wire is connected. That way all metal parts are at the same potential.

 

[zintolo]

Thanks @rkoonce ,

l was thinking indeed to connect the earth to the top plate directly from the dedicated bolt I’ll use to connect it to the rear plate.

Concerning audio ground, for stereo amps with shared PSU one RCA is grounded on the rear plate and that’s it? Better to use the RC 10 Ohm 100 nF rather than go directly to the rear plate?

 

[rkoonce]

I typically keep my earth ground and my circuit ground separated with all input and output connectors insulated from earth. I connect signal ground to earth ground via a pair of 50V 5A diodes wired in antiparallel. That way there's only a diode drop voltage difference between signal and earth. It helps with ground loops.

 

[zintolo]

Thanks again @rkoonce ,
antiparallel diodes are connected from RCA to earth?

I've always grounded the signal at the worst S/N point, that is usually the jack or RCA input.
Generally using the 10 Ohm || 100 nF method. I will try the antiparallel diode method.

I will post a sketch of how I want to manage the grounding.
For sure alot of you have built alot of stereo amps with shared PSU in a wooden chassis.