Ground Loop problem

[jleaman]

Originally posted by Mad_K
I would have tried to connect SG (RCA GND) to the other side of R0 (near Z4).

I'll try that tonight. Any other suggestions.?

[Mad_K]

You should also connect -IN at that point.

[jleaman]

Originally posted by Mad_K
You should also connect -IN at that point.

Im lost with that one.. Canyou draw it out ? Rca in goes to +in and -In is shorted to gnd

[mpmarino]

Originally posted by jleaman



Where do you want the speakers Ground connected to ?

Right where it is already... It wouldn't matter since the speaks are isolated .

[jleaman]

Originally posted by mpmarino



Right where it is already... It wouldn't matter since the speaks are isolated .

OK but just to be sure the speaker ground is the same as the input ground you know that right ?

[mpmarino]

Yes..

I know, ground is ground on this amp. Power/signal/speaker are all the same potential. You could change your speaker ground to anywhere on the chassis that is ground and I don't think it would make a difference. There are 2 speakers, one has nothing to do with the other, therefore there can be no loop associated with the speaker grounds.

Iwould really try a series groung on power and signal. It won't take long, won't hurt anything, and worked for me

[jleaman]

Originally posted by mpmarino
Yes..

I know, ground is ground on this amp. Power/signal/speaker are all the same potential. You could change your speaker ground to anywhere on the chassis that is ground and I don't think it would make a difference. There are 2 speakers, one has nothing to do with the other, therefore there can be no loop associated with the speaker grounds.

Iwould really try a series groung on power and signal. It won't take long, won't hurt anything, and worked for me

I'll tryit tonight see what i com up with. .I dont think it will work but hey it's worth a try.

[Blues]

Originally posted by Mad_K
I would have tried to connect SG (RCA GND) to the other side of R0 (near Z4).

I was looking at the circuit board design and it seems the SG is not utilizing R0 as designed by NP and is not isolated from the circuit GND.

[jleaman]

Originally posted by Blues


I was looking at the circuit board design and it seems the SG is not utilizing R0 as designed by NP and is not isolated from the circuit GND.

Soloution ?

[Cortez]

Not to the humm:
> http://jleaman.ath.cx/aleph/testing-psusm.jpg
The load (the speaker) could have high currents.
If you ground it through the PCB, and that PCB point
will be the signal GND, there can be a problem, namely:
imagine a high current on that green speaker ground wire and
maybe some RFI too, cause the speaker cable acts as antenna too.
And imagine that the green wire from the amp PCB to the PS PCB
has a resistance, and a high frequency impedance. Now when the
high current, and the RFI arrives from the black speaker terminal,
it wont go directly to the main PS GND, but partialy remains, and
that will be the polluted signal GND on the PCB...
So The speaker GND should go directly to the PS PCB, and an other
GND wire should go from the PCB GND to the main PS GND.

> http://www.diyaudio.com/forums/attac...amp=1146205602
So if your speaker GND is now going from the terminal directly to the PS GND,
you should route your output from the amp paralell with the PS rails back to
the PS PCBs top, and then the 2 speaker cable will go from that point to the
terminals. I hope thats clear.

To the humm:
Otherwise on this picture the signal cables are too near to the high impulse AC section,
and if I'm right, there is a great groung loop in the middle, created by the two signal
cables (because at the source the gnds are connected likely) and through the PS GND
wires, there is another connection, so the loop is created, and the PS is in the middle
of that loop.
Try to put the signal cables from the other side, where the built-in RCA-s already are,
and you could try, that the signal GND and the PS GND is connected right from the RCA
to the PS PCB GND, like on my attached picture.

Where your heatsinks are connected to ?
Do you conencted the safety earth somewhere ?
You should try to conenct these together. First trough a wire, and then through
a resistor, then through a series RC, a paralell RC, etc....


Good luck !