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
179 posts
 
U guys think I should just try some different cable?

I seem to be out of options with my current BlueJeans LC1s.
Post removed 
djembeplay OP
179 posts
 
You think so? IDK, it seems weird that just swapping out one of the interconnects fixed everything...

Plus it isn't the typical 60Hz humm.. it's like 2-3 kHz... more of a whine. Also, there is that strange distortion in my lower bass region.

All I can think is there is some sort of interference between 2 BlueJeans cables that are near eachother and have a different magnitude of the same signal going through them (the one after the pre-amp will be attenuated unless it's at full volume).

Sucks...
Post removed 
kijanki's avatar
kijanki
4,433 posts
 
Bob - I asked since I've never had coax interconnect. Grounding shield on both ends is really bad, using shield as return is even worse. In addition coax cables, used in video applications, have not the greatest copper since at high frequencies signal travels only on the surface (often silver plated). Blue Jeans cables can still sound great (I don't question that). Capacitance, they are so proud of (12pF/ft) is nothing special (typical for polyethylene) since best cables have 3.5pF/ft and my cable has 5.1pF/ft. In order to get this capacitance foamed teflon in oversized tubes is required but it's expensive.

I am not talking about ground loops. If transmitting end (let say preamp) has ground/case at different potential than power amp's ground/case then it places this potential on the shield. Shield couples this difference (AC) to signal wire (referenced to different GND). When shield is grounded on the amp side then it has exactly the same level as the reference level of the signal wire and doesn't couple anything.
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