Please help.... Grounding issue, and 60 Hz hum

[PaulHilgeman]

Thaks for all of the replies guys. I will do a frequency analysis on the hum in a little bit. I am pretty sure that it dosnt come from my gainclones, as it only starts as soon as I plug the gainclone into the preamp.

-Paul Hilgeman

[ashwin]

Originally posted by PaulHilgeman
Thaks for all of the replies guys. I will do a frequency analysis on the hum in a little bit. I am pretty sure that it dosnt come from my gainclones, as it only starts as soon as I plug the gainclone into the preamp.

-Paul Hilgeman

In that case, try using shielded cable from the preamp to the amp. I had the same problem (amp unplugged from source was dead silent, but hummed loudly when connected). Ground the shield at one end.

- Ashwin

[PaulHilgeman]

sounds good,

I actually used sheilede cables, but didnt connect the sheild to anything. That works out perfect, huh?!!!

[PaulHilgeman]

Ok... I sheilded my RCA cables, and added in the line filter. The clicks when I change the speed settings on my fan have been reduced. There is much less of a HF click when I change speeds, but there is still a click, maybe with the maximum frequency in the click being about 1000Hz.

The humm has gone way down, probably 10dB or so lower than it was, so low that I cant hear it at all from the listening position, or even from halfway between the listening position and the speaker. The only place that I can actually hear it is within less than 12" from the speaker.

so... thanks guys.

-Paul Hilgeman

[Anorgan]

"We will want to ground the chassis to circuit ground, and for safety it is desirable to also earth
ground the system through the third conductor of the AC line cord. This occasionally results in
ground loop noise, and if it does, I recommend grounding the system to earth through a 10 ohm
5 watt resistor as an alternative to simply floating the chassis."

This is what Nelson Pass had to say about this issue, so there, maybe that helps.

[EC8010]

Originally posted by Anorgan, but quoted from Nelson Pass
"We will want to ground the chassis to circuit ground, and for safety it is desirable to also earth ground the system through the third conductor of the AC line cord. This occasionally results in
ground loop noise, and if it does, I recommend grounding the system to earth through a 10 ohm 5 watt resistor as an alternative to simply floating the chassis."

That is a frighteningly vague statement. Unless you know precisely what you are doing, the chassis must be firmly bonded to the earth conductor of the line cord. We may then choose to connect circuit ground to chassis, possibly via a 10 Ohm resistor to break a ground loop.

[dhaen]

Please also read this thread:
Tension on chassis
It has relevance to 2 pin mains issues, and conformance.

[JOE DIRT®]

EC8010 is correct on his statement

DIRT®

[Jimmy154]

Originally posted by EC8010
That is a frighteningly vague statement. Unless you know precisely what you are doing, the chassis must be firmly bonded to the earth conductor of the line cord. We may then choose to connect circuit ground to chassis, possibly via a 10 Ohm resistor to break a ground loop.

I'm not too good with the techical terms. Circuit ground refers to the PCB grounds? And they both go to a 10 resistor (is 12 ohm okay?) and then to the star ground, where my earth ground goes to the AC line cord. Do I have this correct?

I'm asking because I had a slight buzzing noise from the tweeter and woofer on both channels and I tried to get it to go away. And relised my power strip (that my gainclone is plugged into) had no ground wire where it plugs into the wall (although all the plugs on the power strip have ground wires for some reason). So I plugged my gainclone into the wall and the slight buzz turned into a pretty loud and very noticeable buzz.

[EC8010]

12 Ohm will be fine. Yes, circuit ground is the ground on your PCB. Yes, you seem to have this correct.

You may have a hum loop. If you have two wires connecting at your star ground that connect somewhere else as well, that will form a loop, and could cause hum.