The Dreaded Ground Loop and GPU Whine

[frend2001]

Hi FMs

After having connected the newly acquired ENBEE Pre and power combo to my PC, I faced a strange phenomenon.

Whenever I opened any window on my PC or even moved my mouse over the screen a noise like a motor whine would come from the speakers. Strangely no noise was head when I connected my headphones directly to the PC's audio out.

I did everything that occurred to me like changing the interconnects, changing the inputs jack on preamp and what not, but to no avail.

Finally took to the google baba.

So it turns out many a users faced this issue and it was attributed to 2 things it seems.

The Dreaded Ground Loop and GPU coil noise.

As per online search I had 2 options either change the Motherboard or use 600 OHM transformers in between the interconnect to clear the fuzz.

I paid more attention to the phenomenon of ground loop and could understand some basic things like it's 2 grounds fighting with each other. The ground of PC and the ground of Preamp are not equal and thus the noise.

Well since I could not change the motherboard of my PC, all I could do was to put the 600 ohms transformer in my interconnects. Cutting up the interconnects did not appeal me much and sourcing them transformers was also like I had to order at least a pack of 12 of them.

I was powering the PC, the power amp and the preamp thru the same power strip. I changed the preamp power source to a different wall socket and hey it was gone.

The noise was gone. Completely.

How's that for a riddle ?

It was not there for a week then it came back although I didn't change a single thing in the setup.

Now what ?

I can't stand this noise in background.

My good FMs....pour in.....

 

[jls001]

I had this issue too. The analog audio output from the sound card of my PC which goes to preamp developed a loud hum one fine day. It had been working perfectly fine for years.

The solution that worked for me to put a ground loop breaker circuit in the preamp (buffer, actually). I usually install a ground loop isolation circuitry on all my gears but somehow overlooked the buffer. The ground loop breaker completely cured the problem.

Check out this: http://sound.whsites.net/earthing.htm

All you need are:
1) a 35A diode bridge. Costs about Rs 35-40.
2) 10 Ohm 5Watt resistor
3) 100 nF capacitor rated for 250V or higher
4) Clips that insert to the terminals of the 35A bridge
5) some length of 2.5 sqmm electrical wire
6) one lug, or you can even simply loop the wire

 

[frend2001]

Thanks Jls001.

It was a enlightening read.

Well based upon what I read in the mentioned article I did another experiment.

I disconnected the earth wire from power amp plug.

The noise is again gone. Vanished.

Is it ok to keep earth wire disconnected ?

 

[rikhav]

I am not an expert but I think it's there for a big purpose and rather not disconnect it for if nothing else then for safety

 

[Naturelover]

Is it ok to keep earth wire disconnected ?

A big NO to that.
Ping FM magma. I do believe he had posted something on ground loop a while back.

 

[frend2001]

I had this issue too. The analog audio output from the sound card of my PC which goes to preamp developed a loud hum one fine day. It had been working perfectly fine for years.

The solution that worked for me to put a ground loop breaker circuit in the preamp (buffer, actually). I usually install a ground loop isolation circuitry on all my gears but somehow overlooked the buffer. The ground loop breaker completely cured the problem.

Check out this: http://sound.whsites.net/earthing.htm

All you need are:
1) a 35A diode bridge. Costs about Rs 35-40.
2) 10 Ohm 5Watt resistor
3) 100 nF capacitor rated for 250V or higher
4) Clips that insert to the terminals of the 35A bridge
5) some length of 2.5 sqmm electrical wire
6) one lug, or you can even simply loop the wire

The above components......how to put them together ?

Can you point me to the instructions ?

Thanks

 

[jls001]

The above components......how to put them together ?

Can you point me to the instructions ?

Thanks

See attached diagram. Note the orientation of the four pins of the 35A Bridge. Place the Bridge exactly in same way and you can know which are the AC and DC +/- pins. The pins are fairly large. You can either use clips that fit these pins to wire it up, or simply solder it. I have used both methods and they both work. The hole at the center of the Bridge is suitable for bolting it down to the chassis. I think 4 mm bolt fits. The paint on the chassis must be scrapped off to expose the raw metal so that the ground has proper electrical contact to the chassis. Fasten tightly.

"AC Ground" is the ground wire coming from the IEC socket. If it is already grounded to chassis, you need to remove the existing grounding and insert the Bridge as per the diagram. Note that this involves drilling a hole in the bottom of the chassis to bolt down the Bridge. It is a cure but fairly involved. If you're not confident of doing it yourself, don't do it. You could ask a fellow forum member
with experience to help you with it.

 

[frend2001]

Thanks a ton Jls001.