optocoupler to eliminate ground loop

[ostie01]

Hi that's exactly what I've done.I you look closely, you'll see that the black wire(ground) is connected in the middle of both filter caps.Do you think I should build a single power supply board for both channels.Does it worth a try.

 

[richie00boy]

You should be fine with PSU for each board as long as you star them together properly. Each of these PSUs should have a wire off to the actual main central star ground, usually at the earth screw on the case.

 

[ostie01]

Hi, hope my question will not cause you too much toubles.I have now isolated each boards from the case and attached a wire between each
ground(psu to psu), now the left channel have no hum at all, very clear
but the right channel still have a hum.Will continue to investigate the right channel to find out what's wrong.But I have to confess that I'm a little bit lost.Thanks

 

[richie00boy]

You should not have a wire between each, but a wire from each to the central star point. This point should be located on the chassis, mains safety earth should also connect to this exact same point.

 

[ostie01]

Hi, just one last question please.When you look at the picture,you'll see that all wire that goes from NE5532 output to potentiometer, to output jack are sheilded cable and grounded near were the cable is connected itself, should I remove these sheilded cable and use standard non sheilded wire since my transformer is outside the case.
There's 20 grounded connections per side(10 sheilded cables) not counting input connections,That's a lot of ground connections.Should I have the minimum ground connections i.e. one per boards,one for input and one for output connected together.If you look at center left,I add the star ground like you suggested but maybe there's others things I can do to make it better.Thanks in advance





http://img104.imageshack.us/img104/7471/mycrossover35xx.jpg

 

[richie00boy]

Really the ground on the boards should be input and output ground to the same point. This usually works itself out in practice unless you have a load of inputs and outputs on one board. Even in that case it might not be so bad in practice with low power circuitry. Looking quickly at your pic things look OK.

The sheilded cable is fine and the best way, think of any inputs or outputs as extensions of the board, so you see their ground is best done on the board not back to the star. If you use isolated sockets then everything should be fine as there is no loop.

 

[ostie01]

Hi, thanks for all yours good advices,was a misconception problem,after checking it all following what you said, turn out to be a psu grounding issue, have isolated ground from psu and connected ground from the two boards to star and complete silence, no hum.What an improvement over my last setup with the two rane AC23.
Just want to thank you and everybody posted on my tread.