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
djembeplay OP
169 posts
 
It was caused by the LC-1 using shield as the return? What does this mean? Why was it bad only when connected to my pre-amp? What types of cable should I be looking at as a replacement?

Thanks everyone for the help - much appreciated.
kijanki's avatar
kijanki
3,575 posts
 
Djembeplay - I'm still not sure that cable was the problem. In general using shield as return is a bad thing but in case of hum or interference we enter the area of "black magic". Bob is right about your problem originating in unit being plugged into different outlets but the certain cables can exaggerate this effect. Why can't you plug everything to the same outlet?
tvad
9,467 posts
 
If you want to try grounding your DAC to your preamp chassis, all you need to do is loosen one chassis screw on each component, wrap some wire around the screw, and tighten the screws. The screws function as grounding posts, since the component's electronics are usually grounded to the metal chassis.
djembeplay OP
169 posts
 
I do have everything plugged into the same outlet. It's all on a power conditioner, actually. I think the confusion there arose when I was switching my power plugs around everywhere to see if that would make a difference.

I tried grounding the DAC to the pre-amp chassis earlier but it didn't seem to make the slightest bit of difference. The screws on my DAC are really small, but I made pretty good contact with them.

So, even though LC-1 cables use shield as a return, I still shouldn't have this problem? What exactly does it mean to use shield as return?
tvad
9,467 posts
 
I'm outa bullets.

Good luck.
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