Optimum Gainclone grounding arrangement

[minniedog]

Apologies if this has already been covered, being a beginner the more I read on grounding the more confused I get!

The pic attached shows the grounding arrangement suggested by the supplier of the LM3886 boards I just received. I've read around here that signal and power grounds should be kept separate which doesn't appear to be the case here.

Any opinions on what should be the ideal set-up would be greatly appreciated.

Thanks,

Andy

[thetube0a3]

You know I could be wrong but I would only ground the chassis from the side of the board near the transformer.

[infinia]

1) Use a star ground at the output of PS board, including one chassis connection ie 3 wires total. (speaker out returns may be best connected here as well)
2) Delete chassis connection at input of the PS board and twist the 3 XFMR secondary wires together.
3) Use shielded or twisted wires at RCA input and float chassis ground at the RCA connectors.
4) Mains safety ground wired directly to chassis. Thus there should only be 2 wires tied to chassis including this.

[minniedog]

Originally Posted by infinia

3) Use shielded or twisted wires at RCA input and float chassis ground at the RCA connectors.

Thanks for this, can you clarify what you mean by floating chassis ground at the RCAs?

Like I say, I'm still learning and don't want it all to go bang!

[infinia]

Most panel mount RCA jacks (cinch in UK ) have an insulated bushing to keep the outer conductor from contacting the metal mounting panel, thus floating from chassis ground.

[minniedog]

Thanks, that makes sense.

So, RCA, power and speaker gnd are each connected to the "star"?

[infinia]

Almost, the RCAs run to amps PCB input. Before you hook things up , redraw your diagram with what I said.

[minniedog]

Sorry, I meant input, speaker and power connected to the star.


New suggested grounding in green (I foolishly scribbled on the only copy of the schematic I have!)

I really appreciate your help with this!

[infinia]

nice
The speaker return from the panel shuns the amp PCB and routes directly to the star ground.
so in addition to the grounds, The speaker out has only one wire from the amp PCB and another from star ground on the PS PCB. The input has 2 twisted wires from the amp to the floating RCA.

[digi01]

Originally Posted by infinia

1) Use a star ground at the output of PS board, including one chassis connection ie 3 wires total. (speaker out returns may be best connected here as well)
2) Delete chassis connection at input of the PS board and twist the 3 XFMR secondary wires together.
3) Use shielded or twisted wires at RCA input and float chassis ground at the RCA connectors.
4) Mains safety ground wired directly to chassis. Thus there should only be 2 wires tied to chassis including this.

Star ground is no good for this case.when connected a source,there are big loop between the source left output <-> unbalanced RCA cable <-> the amp left RCA input <-> left amp pcb <-> star ground point <-> right amp pcb <-> the amp right RCA input <-> unbalanced RCA cable <-> the source right output <-> inner source circuit <-> the source left output.this loop is signal level.

So if you set up two or more amp pcb into a single chassis.you have to 'STACK' the ground track on each pcb 'TOGETHER' to pass away the loop between the source & amp.

I think a strong ground bar would be better.

Can you read this thread?
http://www.diyaudio.com/forums/chip-...ml#post1403793


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