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Isolating Digital Noise, need help.

I'm hearing noise from my ARC CDP thru my speakers presenting as a high frequency "whine" or "soft screeching." I need to isolate my digital from the AC line it shares with my analogue components. Running another dedicated line is not an option at this time.

I was wondering if a power strip with isolated receptacles, such as star-grounding, would be an alternative to a separate AC line.
As a test, I now have the CDP connected to a different outlet in my house and the noise thru my system is eliminated.

Would this type of power strip be an effective solution, and if so, I could use some recommendations. I have several layers of Blue Circle power conditioning, so I would need a strip with surge/EMF/RFI protection.
128x128lowrider57
jea48
4,425 posts
 


so far there is no high-pitched noise when using the stock PC on the ARC. Perhaps the Audience PC is not a good design for a digital device?


The IEC connector is probably wired wrong. The Hot and neutral conductors are probably switched, interchanged. You can check it with a meter. Just check for continuity.

Simple way is to use the stock cord that came with the ARC CDP. Check plug blade to IEC contact for feed through continuity. Then compare the Audience PC to that. The ARC stock cord is the correct plug to IEC polarity orientation.


Also, I still need to work on the ground-loop problem between amp and preamp, and that will require a separate AC line.

If both the preamp and power amp are plugged into the same wall outlet duplex receptacle and you get a ground loop hum now, then more than likely you will sill get the same ground loop hum with a dedicated AC line.

Beats me how you can get a ground loop hum from the AC mains safety equipment grounding conductor if only one AC mains system equipment ground is involved. It takes two tangle. Where is the other AC mains system equipment ground providing the difference of potential, voltage, needed for the current flow to produce the 60Hz ground loop hum? No difference of potential, no current flow, no hum. What power cords are you using on the preamp and power amp? Stock, or aftermarket? If aftermarket try the stock cords that came with the equipment.

Is the audio system in any way connected to a Cable TV system or Satellite
dish system?

And what's with the power conditioner? You didn't mention anything about a power condition in previous posts. Try removing the power conditioner and plug the equipment directly into the wall duplex receptacle. Remove the ground cheater, check for ground loop hum.



 

jond's avatar
jond
5,807 posts
 
"so far there is no high-pitched noise when using the stock PC on the ARC. Perhaps the Audience PC is not a good design for a digital device?"

Now that sounds decidedly odd just out of curiosity are you using a cheater plug with both the Audience PC and the stock power cord? Also just wondering what's the output voltage of the ARC? It could still be a gain issue, not saying that the IEC isn't wired incorrectly goodness knows jea48 knows a lot about that subject, but an interactive issue would seem to make more sense equipment mis-design? Or at least more likely considering you've had the ARC long term with no problems until the new preamp showed up.

lowrider57's avatar
lowrider57 OP
5,417 posts
 
@jea48,
Beats me how you can get a ground loop hum from the AC mains safety equipment grounding conductor if only one AC mains system equipment ground is involved. It takes two tangle.
There's been a miscommunication. When I referred to the ground-loop problem, I left out some of the back-story. When I first installed the Atma-Sphere preamp, it was using a 3-prong grounded plug (tried both stock and aftermarket). The amp was using a 3-prong stock cable and both were plugged into the same 20a dedicated line. The result was a 60 Hz ground-loop hum.
I understand the principle of ground-loop in this case because they are connected by an unbalanced line.
The only way to eliminate the hum was to run the preamp with a cheater plug.

The strange part is that my previous preamp (Rogue Audio), was hooked up this way with no hum. Stock 3-prong on amp, Audience 3-prong on preamp, unbalanced interconnect.

In that thread, either you or Al directed me to the Whitlock paper and I learned that the concept of using 2 dedicated lines may not eliminate ground-loop when using unbalanced cables.

There is no cable TV and during this period, the power conditioning was removed.
 I'm going to look for my multimeter tonite.


lowrider57's avatar
lowrider57 OP
5,417 posts
 
@jond, the output of the ARC is high; 2.7V unbalanced. But the Atma-Sphere has a switch for -6dB attenuation on the input.

With the Audience PC, had the cheater on and off; still had the high-pitched noise.
Stock cable, no cheater plug.
jea48
4,425 posts
 

I understand the principle of ground-loop in this case because they are connected by an unbalanced line.
Please explain it to me, because I don't understand it.
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