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.
lowrider57
I'm not a big fan of power strips. Have you considered a small isolation transformer or a small battery regenerator?

Another thought. Do you have a Nordost or Ansuz dealer close by. I ask because you may be amazed how well products like the Nordost QV2/Qk1 and or Ansuz Sparkz TC work. Maybe borrow one for an in home demo if you have an open outlet. I'm not sure if it would cure your whine because I've never run across a 'whine' problem due to power. I have an Ansuz MainzD8 power distribution and it does isolate analog from digital.  

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.

For a test did you try using a ground cheater plug on the ARC CDP? I would suggest you try that first.

It sounds to me from your post the power supply of the CDP is corrupting the power supply/s of the analog equipment. You might look into a power conditioner for the CDP to isolate the CDP power cord from the analog power cord/s.

Does the ARC CDP have a detachable power cord? If so are you using the stock power cord that came with the CDP or an aftermarket power cord?

If it is an aftermarket power cord you might want to make sure it is wired correctly. Make sure the Hot and Neutral conductors AC polarity are not flipped from the plug and the IEC connector.




 

 

Lowrider is this a new problem that cropped up overnight? Is the whine present in both channels? Does your Arc have tubes? Tubes can make some very strange sounds especially when getting microphonic. If it does have tubes try tapping them lightly to hear if the noise changes.
@xti16, good question. I am hearing this noise since I added a new preamp (Atma-Sphere UV-1) which is much more transparent than the previous one and has higher gain.
 What's interesting is that it is so resolving, I can hear the change in noise from the power grid at different times of the day. I have a dedicated line, but live in the city. Late at night, the line is quiet.

It's an ARC CD3 mk II which is SS. And to answer xti16, I use a Jensen Iso-Max transformer to help with a ground-loop issue. It does cut the level of the high-pitched whine, but not completely.
I will be adding a DAC, so I need a plan for expanding my digital and to keep it isolated.

@jea48, yes I've used a cheater plug. You helped advise me on my dedicated line thread, where I wanted to add a line to remove a ground-loop between the amp and the preamp. Since I'm using unbalanced interconnects, the consensus was that an additional line would not guarantee the removal of the ground-loop.
I haven't installed that line yet since the layout of my circuit box is a mess and can't afford the electrical work at this time. So I'm using a cheater-plug on the preamp, as much as I don't like the idea, and a Jensen on the CDP.

My PC on the CDP is an Audience PowerChord, but I can try the stock cable for a test.
lowrider57 you're sure the ARC is the issue? Have you tested other sources just to be sure? And you mention using a cheater plug on the preamp, did you try the cheater before of after you started hearing this noise?
jond, I've had to use the cheater on the preamp from the beginning due to 60Hz hum. Spoke to Ralph at Atma-Sphere and Almarg and the problem is due to ground loop thru unbalanced cables.
The Jensen Iso-Max didn't work on the preamp, there was still low-level hum and it changed the sonics of the preamp.

The ARC is the issue. No noise when using my backup NAD CDP.
Gotcha so this noise from the ARC is new or have you heard it combined with the Atma preamp the whole time?
@jea48, 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 stock PC sounds pretty good thru my power conditioner, but lacks the open soundstaging and depth of an audiophile PC.
I actually have a Synergistic Research Black PC on order for demo.

Since I'll be adding a DAC, I will still need to isolate digital from analogue components. Is a dedicated line the only way?
Also, I still need to work on the ground-loop problem between amp and preamp, and that will require a separate AC line.
jond, yes, I’ve heard it the whole time. It took me a while to track down where it was coming from.

I have excellent upper frequency hearing and there has been a constant high-pitched "whine" in my house whenever my system was powered up. I have tinnitus, so at first I thought it was me. I finally put my ear near the tweeter to find it.


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.



 

"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.

@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.


@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.

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.
jea, I hope that's a rhetorical question, because I'm going by what I read in the Whitlock paper.
Ralph thinks my Sunfire amp may have an atypical grounding design.
Have you tried a cheater plug on your digital-without changing anything else?
ptss,
yes, using cheater plug on the Audience cable from ARC CD will get noise.


jea, I hope that's a rhetorical question, because I'm going by what I read in the Whitlock paper.
Ralph thinks my Sunfire amp may have an atypical grounding design.

No, I did not mean it as rhetorical question at all.

(I assume the ICs are not long.)


I understand the principle of ground-loop in this case because they are connected by an unbalanced line.

Not that I doubt you read it. Where did you find that in the white paper? We are not talking about noise.

  
https://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

I think Ralph is probably right about the Sunfire grounding design and somehow that is causing a difference of potential, voltage, to exist between the two safety equipment grounded chassis. Thus current flow, 60Hz ground loop hum.

Just curious what happens if the ground cheater is placed on the amp and not on the preamp? Did you ever try it that way?  

When you find your multi meter I would also be curious to know, if from the IEC male ground contact pin on the Surfire amp if there is any measureable resistance  from the IEC ground pin to the metal chassis of the Amp. There should not be any resistance. The meter should read short. (Disconnect the ICs from the preamp when do the test. Shouldn't make any difference but it totally isolates the amp from anything else.) 

@jea48,
First, thank you for the tip on checking continuity of the two cables. They both test with a beep using the Continuity Setting.
Using the Resistance setting, both test close to zero.

As far as my understanding of ground loop, when two devices are plugged into mains power (both grounded), then connected together by an unbalanced cable, there will be current running thru that cable to each component. Is this correct?
BTW, the section on audio ground-loops in the Whitlock paper starts on page 56.
jea, I didn't try the cheater on the amp. I didn't think it was a good idea to lift the ground since it is a high power/current amp.

I will test the resistance on the Sunfire tomorrow, good idea. FYI, this amp was built in 1998 and has a fixed 3-prong AC cable. The next generation amp included an IEC cable.
Hi Lowrider,

I’ve just read through this thread. First, let me summarize some of the key points I’ve perceived:

1)The problem does not occur in any of the following cases:

(a)The CDP’s stock power cord is used instead of the Audience power cord.
(b)The CDP is connected to a more distant outlet. When you did this, how was the connection implemented (e.g., with a long extension cable attached to the Audience cord)?
(c)A different CDP is used.
(d)A different preamp (the prior one) is used.

2)The CDP’s stock power cord does not provide the open soundstaging and depth of the Audience power cord.

3)You will be demo’ing an SR power cord.

4)No ground loops are present, because:
(a)There is a Jensen transformer between the CDP and the preamp.
(b)There is a cheater plug on the preamp’s power plug, which eliminates the possibility of a ground loop between the preamp and the power amp.

5)Ideally you would prefer a solution that in addition to resolving the issue isolates the AC power provided to the digital components from the AC power provided to the analog components, because you anticipate purchasing a DAC.

Questions and suggestions:

1)If you haven’t already, it might be worthwhile trying the CDP’s stock power cord on the preamp. 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, that is causing the problem by coupling into the preamp through its power cord. So perhaps putting the CDP’s stock power cord on the preamp would resolve the problem, while not causing the sonic degradation you observed when using that cord on the CDP.

2)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?

3)For that matter, how close is the CDP to the preamp, and if they are close together have you tried moving them further apart? Although it seems likely that the noise is coupling through the power wiring, I don’t feel 100% certain of that at this point, and I wouldn’t rule out the possibility that radiated interference is contributing.

4)Regarding power isolation or filtering between digital and analog components in anticipation of obtaining a DAC, my feeling is that perhaps you should cross that bridge when you come to it, and not necessarily as part of the process of resolving this problem. For one thing, the optimal approach at that time may be DAC-dependent, requiring greater or lesser degrees of isolation or filtering depending on the particular DAC. And who knows, it may not even be necessary to provide any.

Good luck. Best regards,
-- Al

lowrider57, I think that others may have already suggested what I would do first. 

Disconnect the interconnects from the amp and turn it on, If there is no noise, it is something upstream. If it still hums it is the amp, of course. 

Next add the line stage with both it and the amp on. If it doesn't hum, it is the line stage. If still no hum it is one of the sources. 

If it doesn't hum with one source but not the other, well you know. I think  you may have already done this and suspect the digital source. I would put a cheater plug on the amp if you find it is the digital source. If no hum with the cheater, you have ground loops. I would use cheaters on everything except the line stage.
Possibly the Blue Circle FX2XOE (that has 3 pair of outlets) would filter out the problem. The only reason I'm suggesting this is because I use one to correct a problem I had in my secondary system. It worked out so well, I purchased a second one that is brand new but I have not needed to use it. If other suggestions don't work you could try mine.

@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.
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.

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?

@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.

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?

I hooked up the Pangea PC to the ARC CDP and I'm getting the same high-pitched noise as with the Audience cable.
 After several A/B tests, there is noise when using the stock PC, but less audible than with aftermarket cables.

So it leaves me to wonder if I should try an isolated power strip. Right now all my components run thru the Blue Circle and then to a Furman EMF/RFI strip except for the amp. Or is there a filter or power cord for digital devices?

Do you get any noise when only the amp is in the system and on, of course?

Is it possible to try a different outlet without the extension cord?
@tbg , no, amp is quiet.

@jond, I'll try that today, the cable from the Furman may reach across the room.
Thanks.
Lowrider, I had previously suggested trying the CDP’s stock power cord on the preamp. However, given that it is now evident that the CDP’s stock power cord doesn’t fully eliminate the problem when used on the CDP, what I would suggest is that you try connecting the CDP with the Audience power cord in series with the long extension cable (which eliminated the problem when plugged into a distant outlet), plugged into the **SAME** AC socket you normally use for the CDP.

And if that resolves the problem but also results in any adverse sonic effects, try putting the extension cord in series with the preamp’s power cord instead, plugging it into the same place as usual.

Keep in mind that when you eliminated the problem by connecting the CDP to the distant outlet you changed two things at once, namely using the distant outlet, and putting the extension cable and its undoubtedly significant inductance in series with the CDP’s power cord. At this point we don’t know which of those variables eliminated the problem, but it very conceivably could be either of them (or both).

Best regards,
-- Al

@jea48
Check again for resistance from the ground pin on the power cord plug to the metal chassis of the amp. "OL"?
Yes, OL (or zero L). Maybe a code for something?

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?
  1.0 for resistance.

I have looked on Carver/Sunfire forums for a schematic and no luck. Others are asking for them and apparently the company has never released them to the public.
Many thanks for interest thus far. 

Yes, OL (or zero L). Maybe a code for something?

If you do not measure 000.0 or in otherwards "short", or continuity, then for some reason the metal chassis of the amp is floating above the safety equipment ground. That does not meet any equipment electrical safety standards/requirements.

What is odd though, from your measurements, the safety equipment grounding conductor of the power cord is connected to the signal ground. You measured 1 ohm of resistance. Correct? That’s basically "short".

Have you ever removed the top cover from the amp before? If you can remove the top cover,. then look at the back where the power cord enters the back panel. Look for the green equipment ground wire of the power. Is the wire broken free from the metal chassis? It should connect directly to the metal chassis.


One other test measurement I should have had you check. From what you have said thus far the result should already be known. I still would like to have you check. Check for continuity from the outer contact of one of the RCA input jacks to the metal chassis. It technically should read "short", "000.0", continuity. But from what you have said from the measurements you have taken, you should read "OL" open circuit. The signal ground is not connected to the metal chassis.

IF the chassis if floating above the signal ground as well as the safety equipment I would think that could cause buzz/hum problems.

And then there is the coupling capacitance leakage of the primary to secondary winding to consider.


Is this what your amp looks like?
https://www.google.com/search?q=sunfire+stereo+amplifier&rlz=1T4GGLL_enUS413US413&tbm=isch&a...


http://s26.postimg.org/j4ws3i4jd/Sunfire_002.jpg


I assume you have the jumpers installed in XLR female connectors.
http://img.usaudiomart.com/uploads/large/689209-sunfire_stereo_power_amplifier_300_wpc.jpg

Thanks, jea48.
First of all, that is my amp...Sunfire 300 Load Invariant.

What is odd though, from your measurements, the safety equipment grounding conductor of the power cord is connected to the signal ground. You measured 1 ohm of resistance. Correct? That’s basically "short".
That's correct. The digital scale measured 1.0 ohm +or- a couple units since the probes were hand-held. It never approached zero.

I've never had the top off, but it was serviced 3 years ago and maybe the wire could have come off. I'll have to wait til I have some time to devote to opening it up since the amp is not easily removed from my rack. I built a custom shelf for it.

Check for continuity from the outer contact of one of the RCA input jacks to the metal chassis. It technically should read "short", "000.0", continuity. But from what you have said from the measurements you have taken, you should read "OL" open circuit. The signal ground is not connected to the metal chassis.
I will do this tomorrow. It seems that you and Ralph are right about the amp not being properly grounded.

I assume you have the jumpers installed in XLR female connectors.
I've never heard any mention of using jumpers on this amp; not in the manual or on Carver/Sunfire forums. Can you explain?

I know that this amp is SE and the RCA and XLR are wired in series. The next generation of the 300 amp is supposed to be fully balanced and has specs to indicate this.
My amp only has a single input sensitivity of 1.64V.
Well, I have some test results to report.
I used an AC receptacle across the room as a second line to separate the components from the amp. It is a shared circuit with ground.
The amp was plugged into it’s dedicated line and the Furman strip with preamp (using cheater-plug), and CDP was plugged into this 2nd line. Both components using Audience PC’s.

1. The result was no high-pitched noise from the CDP. This was tried with the Jenson transformer in-line and also removed. Result was the same; a quiet tweeter.
So, I believe this proves that the ARC CDP is introducing noise into the shared dedicated line and needs to be isolated.

2. Ground-loop issue: used a 3-prong PC from the preamp into Furman and into 2nd AC line.
The amp is plugged into dedicated line with 3-prong (usual setup).
The result was a low-level hum thru the speakers and not the loud 60Hz hum.

The amp is now known to have a grounding issue, but is it possible that that this low-level hum could be due to the fact that the second line’s grounding is unknown?
IOW, I think it is worth running another dedicated line. Ideally 3 lines would be best, but cost is an issue.

Your thoughts?
I believe this proves that the ARC CDP is introducing noise into the shared dedicated line and needs to be isolated.
Yes, but per my previous post perhaps the extension cord itself would provide sufficient isolation, when plugged into the outlet that is normally used. Seems worth trying, on both the CDP (the source of the noise), and the preamp (which is probably where the noise is causing the trouble).
The amp is now known to have a grounding issue, but is it possible that that this low-level hum could be due to the fact that the second line’s grounding is unknown?
That is very conceivable. Jim (Jea48) has previously provided us with a link to a paper by Bill Whitlock (the Jensen Transformer person, although he may be retired now) in which it is explained that ground loop hum is usually caused or contributed to by coupling of EMI between the hot & neutral wires and the safety ground wire in the house wiring. Which occurs very minimally with Romex, due to its symmetrical design, but occurs to a much greater degree with wires in conduit. Is there any way to determine what kind of wiring is used between that outlet and the breaker panel?

Also, Jim (Jea48) makes a good point about jumpers. Given that there is no balanced/unbalanced switch on the amp, and that it has an unbalanced internal signal path, I suspect that jumpering pins 1 and 3 together on each XLR connector might be helpful, with respect to hum and/or sonics. Check for continuity between the center pin of each RCA connector and pin 2 of the corresponding XLR connector. Also check for continuity between the ground sleeve of each RCA connector and pin 1 of the corresponding XLR connector. I suspect you’ll measure close to zero ohms in both cases. If so, I would suggest that at some point you obtain some solid core wire of a gauge that would provide a snug fit and use it to jumper pins 1 and 3 on each XLR connector.

BTW, "OL" is most likely derived from either "out-of-limits" or "overload," and when you are measuring resistance signifies that the resistance is greater than the 20 million ohm upper limit of what the particular meter can measure. In other words, an open circuit.

Best regards,
-- Al

thanks Al. Will do tonight.

ARC CD2 wiring schematic wiring diagram.

http://www.audioresearch.com/ContentsFiles/CD2%20Sch%20pl%20tips.pdf

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XLR shorting jumper.
http://www.cardas.com/images/cgsp_pic1_transparent.jpg

>>


Decoupling the power supply of digital from analog.


Quote from the late Robert Crump:

Solid core Romex has an absolute ton of inductance and you can use that to roll off the digital backwash and end up isolating your analog from digital with yards of the solid core Romex in the walls. Romex is insulated with PVC and, again I will say that PVC is what you want rather than anything faster as you just want to pass 60hz and attenuate anything above that.....Stranded wire, especially a twisted lay, will pass high frequencies better, exactly what you don’t want to do with 60hz AC.......Regarding power cords made with PVC it apparently works pretty well as have sold over 8,000 of them the past 21 years.......

You aren’t looking at this correctly........ - rcrump - Cable Asylum »


lowrider57 said:
@jond, the output of the ARC is high; 2.7V unbalanced. But the Atma-Sphere has a switch for -6dB attenuation on the input.

Al,

What are the chances the ARC CDP is still over driving the L & R input stage of the preamp?

Also look at the ARC CDP output section. Transformers are used.
http://www.audioresearch.com/ContentsFiles/CD2%20Sch%20pl%20tips.pdf

Does that mate well with the input section of the preamp?







Thanks, Jim (Jea48). Note, though, that the transformer coupled outputs shown on the schematic you linked to are the digital outputs, not the analog outputs which Lowrider is using.  Although that schematic is for the CD2, rather than the CD3 MkII he is using.

Regarding overload, the UV-1 doesn't appear to have an input overload point specified, but I'd be surprised if it couldn't handle 2.7 volts.  And even more so given that it provides a 6 dB input attenuator.  And in any event, if it were overloading I'm sure Lowrider, who is clearly a very perceptive listener, would have noticed the distortion that would have resulted.

Regarding Mr. Crump's statement, I would add that in the case of most power amplifiers, at least, one certainly does NOT want to attenuate everything above 60 Hz. As has been pointed out in past threads by Ralph/Atmasphere among several other members, since most power amplifiers draw current in narrow high amplitude spikes, rather than continuously throughout each period of the 60 Hz waveform, their AC supply needs to be provided in a manner that is not bandwidth limited below something on the order of tens of kHz. That requirement being one of the reasons upgraded power cords can often provide superior performance compared to stock power cords, for power amplifiers at least, because many of them provide significantly greater bandwidth than most stock power cords.

Also, I just Googled "inductance of Romex" and found a not necessarily authoritative post in a thread elsewhere stating that it is about 1.45 uH (micro-Henries) per foot.  That is indeed high, but for run lengths that are not particularly long I suppose is probably low enough to be compatible with the kinds of bandwidths Ralph refers to, perhaps depending on the particular amplifier.  While at the same time being high enough to provide significant attenuation of digital noise, which typically has a good deal of its frequency content in the MHz range and higher.  

Best regards,
-- Al
 

Al,

I guess I must have been having one of my brain fart moments.


Try this ARC CD3 MK2 schematic wiring diagram.


http://www.audioresearch.com/ContentsFiles/CD3%20II%20sch%20%20PL.pdf


Jim

Thanks Jim. As with the CD2 only the digital outputs are transformer coupled. And I don’t see any issues with the unbalanced analog outputs Lowrider is using, or with using a Jensen transformer between those outputs and the preamp (assuming cable capacitance at the output of the transformer is kept low, which I believe he is doing).

Best regards,
-- Al

Al and jea48,
I really appreciate the time you've devoted to my situation.
I was out all day, but was able to take some measurements:

- continuity of RCA outer sleeve to metal chassis... reads OL
- continuity of each RCA center pin and pin 2 of XLR... OL
- continuity of RCA outer sleeve and pin 1 of XLR... 000.0

Al, I looked at the 20a dedicated AC line and it appears to be a 12/2 generic cable. I looked at the electrician's invoice from years ago and it is itemized as a Refrigerator line, dedicated 20a circuit.
If you recall, I had a thread where I asked for advise on the proper installation of a dedicated line. That's when I discovered that the electrician placed this wiring near the top of the circuit box and close to the furnace and appliances. So, when I add another line, I will need to have the box reconfigured.

And jea, thanks for the pic of the Cardas jumpers. I found them online and will order them.

- continuity of RCA outer sleeve to metal chassis... reads OL
- continuity of each RCA center pin and pin 2 of XLR... OL
- continuity of RCA outer sleeve and pin 1 of XLR... 000.0

- You said in an earlier post you checked for continuity from the ground pin of the power cord male plug to the metal chassis of the amp and the meter display read "OL"..., Open, no connection. Correct?

IF the RCA jack outer sleeve to the metal chassis reads OL then the signal ground is not connected to the chassis. You said in an earlier post the safety equipment grounding conductor of the power cord is not connected to the chassis either.

I will have to search the archives of AA for a post of Charles Hansen, owner of Ayre Acoustics, but that’s a no no. Something about capacitive feedback loops. Or something like that. At any rate I think it can add hum/buzz on the signal of the amp. (Without rereading all this thread, did you ever have the amp turned on without anything connected to the inputs of the amp? That thing should hum/buzz like crazy I would think. Especially if a ground cheater was used on the amp plug to wall receptacle.)

I am still confused why you measured 1 ohm of resistance, basically continuity, from the ground pin on the plug of the power cord to the outer sleeve of the RCA on the amp. That means the signal ground of the amp is connected to the equipment grounding conductor, wire, of the AC power cord.

You really need to address the problem/s with the amp first before you do anything else. You need to pull the top cover and see why the safety equipment ground of the power cord is not solidly connected to the metal chassis of the amp. Why it, the safety equipment ground wire, is some how connected to the signal ground. Both the signal ground and safety equipment should be connected to the metal chassis of the amp.

(Note: I see no user ground lift switch on the back rear panel of the amp for user preference.)

Jim (Jea48), you provided an excerpt and a link to Mr. Hansen’s statement in the last post on this page. However, I would not interpret his statement to mean that signal ground should be connected **directly** to the chassis, as that can be conducive to ground loop issues. Preferably signal ground should be connected to the chassis through a low value resistor (e.g., 10 to 100 ohms). As you’ve probably seen, for example, a lot of ARC designs use 10 ohms.

My VAC amp, btw, has a three position switch controlling that connection. One position connects signal ground and chassis directly; one position is described as connecting them at audio and higher frequencies but not at DC (presumably via a high value capacitor, perhaps in combination with a resistor); and one position is described as connecting them only at RF frequencies (presumably via a low value capacitor, perhaps in combination with a resistor). The AF and RF positions seem to sound slightly better in my system than the DC position, and I’ve settled on the AF position (which the manual recommends as the one to start with).

In any event, it is strange indeed that the Sunfire amp connects signal ground and safety ground together but not to chassis. If it happens to be connecting the grounds to chassis via a capacitor, though, it would explain why the meter reads OL between the grounds and chassis. But it still would not explain the safety issue that would presumably result from the lack of a direct connection between safety ground and chassis.
continuity of each RCA center pin and pin 2 of XLR... OL
Check for continuity between the RCA center pin and pin 3 of the XLR connector. If that measures near zero ohms, you would want to put the jumper between pins 1 and 2 of the XLR connector.

If that also reads OL, however, it would probably mean that the XLR and RCA inputs are received by separate receiver stages, in which case it would be ideal (although perhaps neither necessary nor practical) to jumper both pins 2 and 3 to pin 1. Or, in that situation (both pin 2 and pin 3 read OL relative to the RCA center pin) you could try jumpering each possible combination of two pins together (1 to 2; 1 to 3; 2 to 3), assessing the three possibilities one at a time.

Best regards,
-- Al



Jim (Jea48), you provided an excerpt and a link to Mr. Hansen's statement in the last post on this page. However, I would not interpret his statement to mean that signal ground should be connected **directly** to the chassis, as that can be conducive to ground loop issues. Preferably signal ground should be connected to the chassis through a low value resistor (e.g., 10 to 100 ohms). As you've probably seen, for example, a lot of ARC designs use 10 ohms.

Al,

Thanks for pointing that out. When the equipment uses the safety equipment ground the designer of the equipment, in most cases would not connect the signal ground directly to the chassis. Arc uses a 10 ohm resistor as well. Somewhere in the thread Link you provide I think I mentioned that.

Here again is the actual statement of Charles Hansen's 


The only way that the case can provide any shielding for the audio circuitry is if it is connected to the signal ground. In addition, if it is left unconnected from the signal ground, then it will create unwanted capacitive feedback loops (both positive and negative) between various parts of the circuitry. Refer to Morrison's books for additional details.

 
http://www.audioasylum.com/audio/general/messages/52/525622.html 

Here is the entire AA posted message. 
http://www.audioasylum.com/audio/general/messages/52/525276.html



In any event, it is strange indeed that the Sunfire amp connects signal ground and safety ground together but not to chassis. Although if it happens to be making the connection to chassis via a capacitor, it would of course explain why the meter reads OL.

UL says the equipment ground must be connected, bonded, directly to the chassis doesn't it? Of course we don't know if the Amp is UL Listed, or was safety tested by any recognized third party testing laboratory.

Off subject,  I was on another audio forum last week and learned there is a well know US audio manufacture, (I will not mention the name here), that provided a ground lift switch on the back of one of his amps. The switch doesn't lift the signal ground from the chassis. It lifts the safety equipment ground wire from the chassis. Obviously the amp is not Listed by any recognized third party testing laboratory.

Jim

Thanks, Jim. Regarding ...
UL says the equipment ground must be connected, bonded, directly to the chassis doesn’t it?
... Shortly after submitting my post, and shortly before you responded, I revised the paragraph you quoted from as follows:
In any event, it is strange indeed that the Sunfire amp connects signal ground and safety ground together but not to chassis. If it happens to be connecting the grounds to chassis via a capacitor, though, it would explain why the meter reads OL between the grounds and chassis. But it still would not explain the safety issue that would presumably result from the lack of a direct connection between safety ground and chassis.
Best regards,
-- Al

jea48 and Al,
Checked continuity between RCA center pin and pin 3 XLR... OL
Same as the previous test for RCA to pin 2 XLR... OL

CDP...
I used the 25 ft. heavy-duty ext. cord with the Audience PC plugged into the Furman strip with preamp today and into the dedicated line, (no power conditioner). The high-pitched noise presented after the components were warmed up. The noise was not as loud, but is still audible.
Tried it with and w/o Jensen Isomax at CDP's output. The Jensen does lower the level of the noise, but it's still objectionable.

jea, since you commented on the high gain of the CDP (2.7V), I checked it by playing thru a different preamp input and the gain is too high. Ralph put in the -6dB pad for me as a mod due to the CDP's high gain spec. And it sounds very good.

As far as the readings I'm getting, do I need a better multi-meter?