2. amps-preamps
  3. 1236409165

Strange ground loop...?

Hey,

I just hooked up a new amp and I'm having a strange noise issue. Only in my right channel, I get this high-pitched whine... maybe around 2khz. My left channel is dead silent.

The problem seems to be an interaction between my DAC and my amp. If the DAC is off, the amp is silent.

The amp is an 84' yamaha, so the cord has no ground. There is a ground screw, though, and I have connected that to my power conditioner, hoping this would solve it... nope.

I've tried plugging the amp straight into the same outlet that the power conditioner is plugged into (into which the DAC is plugged in). That actually did work... but I don't want to run my amp straight into the wall.

I suspect I just need to find a proper place to run that ground wire...

Any ideas?
djembeplay

Showing 6 responses by jea48

jea48
2,944 posts
 
I just hooked up a new amp and I'm having a strange noise issue. Only in my right channel, I get this high-pitched whine... maybe around 2khz. My left channel is dead silent.

The problem seems to be an interaction between my DAC and my amp. If the DAC is off, the amp is silent.
At some point in your trial and error testing did switch, cross, the ics at the amp? (Switch the right with the left at the Amp, one end only of the ics.) See if the buzz then goes to the other channel of the amp. This will kill two birds with one stone, so to speak, the Dac as well as the ics.

The amp is an 84' yamaha, so the cord has no ground. There is a ground screw, though, and I have connected that to my power conditioner, hoping this would solve it... nope.
The amp, I assume, has a built-in phono preamp. The ground screw is for the ground wire of a TT, not to connect the amp to earth ground.

Is the plug on the cord of the amp polarized? One blade wider than the other? Can you plug the plug into the wall receptacle in either direction?

I suspect I just need to find a proper place to run that ground wire...
I would not recommend connecting the chassis of the amp to earth ground.... It can cause more harm than good.

jea48
2,944 posts
 
Hmm, no phono in... just a pair of RCA's. It's a Yamaha M-40 power amp.
03-07-09: Djembeplay
LOL, sorry about that.... I must have had a brain fart, LOL.
For some reason I was thinking preamp in regards to the ground screw...
DAC > to > preamp.....

At any rate I would not connect the chassis of the amp to earth ground.

As for the non polarized plug it might be worth your time to check for the proper AC polarity orientation for the power transformer of the Amp. http://www.boundforsound.com/tweak.htm
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Glad to hear you found the source of the buzz.
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jea48
2,944 posts
 
Djembeplay, Do you have another source you could try in place of the DAC... Tuner? Maybe a DVD/CDP player?

I suggest you try that first. Then if the whining interference noise is still heard you might try contacting Blue Jeans Cable and see what they have to say.....
jea48
2,944 posts
 

03-11-09: Bob_reynolds
According to the OP
I've tried plugging the amp straight into the same outlet that the power conditioner is plugged into (into which the DAC is plugged in). That actually did work... but I don't want to run my amp straight into the wall.

This is the first test to determine a ground potential difference, i.e., ground loop. This is the problem - not the ICs.

Bob did you miss this post of Djembeplay?

03-11-09: Djembeplay
Another update -

I just swapped out one of the BlueJeans ICs with an old Monster IC I had and the problem is completely gone... no whining or distortion at all.
jea48
2,944 posts
 

The problem seems to be an interaction between my DAC and my amp. If the DAC is off, the amp is silent.
Djembeplay
Bob going back to this statement of Djembeplay.
If it was a ground loop hum problem wouldn't the hum still be present with the DAC turned off?
jea48
2,944 posts
 

03-11-09: Djembeplay
I just wanted to add... this distortion, again, completely goes away with my pre-amp turned all the way up.
That rules out ground loop hum imo.....

Humor me and try another source other than the DAC.
I think the problem is the DAC
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