Small humming, but want's to get rid of it !

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2Bak

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#1
I read is this post the below quote from Alcaid: http://www.diyaudio.com/forums/showthread.php?s=&threadid=29489

Alcaid said:
...And another thing; the OUT-GND must go to power-ground not signal-ground.
Click to expand...

Should signal ground and pwr-ground not be connected in an IGC...??

I my pcb (poweramps only) I have a little bit of humming, and I can't figure out where comes from. The amp doesn't hum at all, when interconnects' are not plugged in. Complete silence 🙂
I have two wires (the grey ones) to connect pwr-ground and signal-ground to common starground.
At the moment those two grey wires are of same thickness, perhaps I should make the wire from the signal thinner, however this doesn't make sence to me, cause no current runs in ground...?

I've read many places that out-gound and in-ground should be connected....?

Please give me a hint where I should look for the cause of my humming.

Thread with my pcb's

/Jan
 

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#3
matjans said:
does it hum with all interconnects? If so, it might be a ground loop between your CDP and amp.
Click to expand...

It's a four channel gainclone pwr-amp, e.i. two sets of interconnects, and input comes from a Thule surround preamplifier's output, and hum is there with all kinds of sources in the preamp - dvd, cd, tuner, etc.

If I disconnect the one set of interconnects (only two channels running), no difference....still humming in the two channels which have signal in.

And if I don't use the preamp at all, and instead connect a cd-player with variable output directly to the GC I still have humming.

I've tried everything. Connecting grounds between all four RCA's inside the CG, connecting starground between all four channels, doing chassis ground with 100R's, and much more combinations... But unsuccessfully.

How would one cure a ground loop between source and amp?

/Jan
 
#5
this may seem like a strnage connection, but can you try and disconect the ground sheild on the RCA inputs, so that only the signal pin is conected to anything, as there may be significant currents trying to flow through the screen if your amp and pre's chasis are at different potentials.
 
#6
bigparsnip said:
this may seem like a strnage connection, but can you try and disconect the ground sheild on the RCA inputs, so that only the signal pin is conected to anything, as there may be significant currents trying to flow through the screen if your amp and pre's chasis are at different potentials.
Click to expand...

Would there be any danger to my GC/speakers trying this experiment? FYI none of my equipment use AC ground.
 
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