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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
lowrider57's avatar
lowrider57 OP
5,417 posts
 
@jea48
I did some tests on the amp. With my multi meter, measuring from the male ground pin on the Sunfire amp to the metal chassis of the amp, I could not get a reading of resistance. The meter indicated “L.”
It is a digital meter with no multiplier for scale.

Bypassing all power conditioning, I plugged the amp 3-prong into the wall, and plugged the stock preamp 3-prong cable into the wall; result was 60hz hum. I used Belden Interconnects instead of audiophile brands.

Using a cheater plug on the amp plugged into the wall and stock preamp cable plugged into wall, I can hear a noisy power line when I put my ear up to the speakers.
FYI, there is no transformer hum emanating from this amp.
lowrider57's avatar
lowrider57 OP
5,417 posts
 
Hi Al,
Addressing the CDP high-pitched noise issue:
You are correct. I will provide some further info;
The CDP is connected to a more distant outlet... I used a heavy-duty extension cord with the Audience PC and ran it to a dedicated receptacle for the washer/dryer in the basement. So it was about a 25 ft. run.
I will do this test again with a closer outlet, but they are all typical shared AC lines found in the home.

Regarding ground-loop:
Correct.
The Jensen does remove some of the high-pitched noise. Removing the Jensen is when the noise is at a high level and can be heard thru quiet passages of Classical music.
The reason I remove the Jensen is because the input IC affects the sonic signature of the CDP plus Purist Audio output IC. I am continuing to experiment with ICs for the Jensen input, but the timbre of my system is best w/o the Jensen and a cheap cable. I’m dealing with a double-edged sword.

A reasonable speculation would be that the CDP’s stock power cord, as well as the extension cord I presume you used when you connected the CDP to a different outlet, resulted in higher series inductance than when using the Audience cord into the normal outlet, which in turn provided some degree of filtering of high frequency digital noise
You’re probably right, that’s why I’ll repeat my test using a closer outlet. I used the basement receptacle because it is a dedicated line that I trust.

Are you sure that when you changed between the Audience and stock power cords on the CDP, and when you tried connecting the CDP to a distant outlet, that the physical proximity between those power cords and the preamp was not changed significantly? And that in all of those cases the CDP’s power cord has not been positioned close to the preamp or to the preamp’s power cord or interconnect cables?
No change in position, and power cords are separate from audio cables. But the preamp and CDP PCs are definitely close to each other.

how close is the CDP to the preamp, and if they are close together have you tried moving them further apart?
The CDP is on the top of the wood rack unit (position #1), the preamp is on the 3rd shelf (position #3). Ralph and I discussed placement when I called him regarding hum/ground-loop. The preamp is not in proximity to any transformers.

Al, I appreciate the time you’ve spent on this. I would really like to find the answer to this digital noise problem. I just realised that I have a Pangea PC that I’m not using...this will be my next test on the CDP.
jea48
4,425 posts
 

Lowrider57 said:
I did some tests on the amp. With my multi meter, measuring from the male ground pin on the Sunfire amp to the metal chassis of the amp, I could not get a reading of resistance. The meter indicated “L.”

"L" ? What does the meter indicate when both test probes are touched against one another? "L"? There in as "short" or "000.0", continuity?

>>


Lowrider57 Said:
Bypassing all power conditioning, I plugged the amp 3-prong into the wall, and plugged the stock preamp 3-prong cable into the wall; result was 60hz hum. I used Belden Interconnects instead of audiophile brands.

To be 100% clear here, you did say the ground loop hum is being caused when only the preamp amp and amp are connected together by ICs. Is that correct? The CDP is not in the ground loop, possibly being the culprit causing the ground loop hum, correct?

To be 100% sure that is the case, disconnect the CDP ICs from the preamp and check for ground loop hum. (Ground cheater not used on preamp or amp.)


>>


For clarification.... You said earlier when you used the stock cord that came with the CDP the high frequency "whine" sound was gone. Where was the CDP fed from then? From the basement laundry room receptacle, or from the receptacle by the audio system where it normally is plugged into? I guess I was under the impression it was plugged in the audio system wall outlet when you switched to the stock power cord.


>>

Lowrider57 said:
First, thank you for the tip on checking continuity of the two cables. They both test with a beep using the Continuity Setting.

Continuity? What I want to know are the plug to IEC pin out connections
for the aftermarket power cord, the same as the ARC stock power cord?

lowrider57's avatar
lowrider57 OP
5,417 posts
 
@jea48,
What does the meter indicate when both test probes are touched against one another? "L"? There in as "short" or "000.0", continuity?
touching probes together shows 000.0 continuity.

I made a mistake, it always indicates "0L" when there is no reading.
I downloaded the manual for the meter.
https://equus.com/Content/Support/Manual/93-0041.pdf

What I want to know are the plug to IEC pin out connections
for the aftermarket power cord, the same as the ARC stock power cord?
the same.

To be 100% clear here, you did say the ground loop hum is being caused when only the preamp amp and amp are connected together by ICs. Is that correct? The CDP is not in the ground loop, possibly being the culprit causing the ground loop hum, correct?
Correct. CDP is not connected to inputs.

You said earlier when you used the stock cord that came with the CDP the high frequency "whine" sound was gone. Where was the CDP fed from then? I guess I was under the impression it was plugged in the audio system wall outlet when you switched to the stock power cord.
Yes, the stock PC was connected to the wall behind the system.
jea48
4,425 posts
 

Lowrider57 said:
I did some tests on the amp. With my multi meter, measuring from the male ground pin on the Sunfire amp to the metal chassis of the amp, I could not get a reading of resistance. The meter indicated “L.”

So "OL" equals open? Same as the meter reads with the probes not connected to anything?

Check again for resistance from the ground pin on the power cord plug to the metal chassis of the amp.  "OL"?

Next measure from the ground pin on the plug to one of the outer grounds of one of the RCA jacks on the back of the amp. (No ICs connected to the inputs of the amp.) Any resistance? "OL" ?

What is the model number of the amp? Do you have a wiring schematic diagram for the amp?

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