Head-Fi.org › Forums › Equipment Forums › Computer Audio › USB DAC Suspected Ground Loop Issue
New Posts  All Forums:Forum Nav:

USB DAC Suspected Ground Loop Issue

post #1 of 25
Thread Starter 

Hi!
Issue: I recently started to get some static noise, sounding like my HDD and a ticking sound every second through my DAC. This noise is not present when other signals not from the PC are being sent through the amp. The noise is also present when outputting from front audio and back panel audio out. It can only be heard through the amp and speakers, not headphones. I've even tried MTH-m50's at full and couldn't hear it.

Background: I have recently moved my system from an old case to a Fractal Design Arc Midi R2, and have had a graphics card failure which has been replaced. Since changing the case (which also happened shortly after moving houses) the DAC developed this noise. You can hear it when listening to most music.

Specs:
DAC Destroyer
Case, Arc Midi R2
HD7850,
i5 2500k
P8H67mLE
XFX 550W Pro PSU
3HDD's
1 Bluray.

Amp: JA-S31 powering a pair of Mission 731's. Fed by 5 meter 3.5mm to RCA

So far I've disconnected all HDDs, all connections to the front panel, all USB devices bar this one, this reduced the noise but it was still there, including the ticking. Moved it around through all USB connections, front and back. I have tried disconnecting the fan controller, which affected noise a bit. But they all still leave the ticking and a noise which can be heard listening normally,
Testing the DAC itself through a laptop the noise is not present (on battery anyway, but that's a well known ground loop issue anyway).
The amp is on a different mains loop itself to the computer, both are going through surge protectors and 1 extension cable.

I'm at my wits end trying to figure this out. I'm fairly sure its the case, but all the cases cables seem better isolated than those on the old one. The only alternative is a USB2ISO, and that's currently too expensive for me atm.

I could try ferrite cores around the RCA cable, but I've heard ferrite cores do not work well with USB cables carrying audio. Could try a better USB cabled with better shileding, but what brand?

Any ideas to try?


Thanks!

post #2 of 25

When you changed cases, you changed power supplies too, right?  These issues are almost always power supply related.  If you can get your old PSU into the new case, give that a try.  

 

You can also try running a piece of wire from the chassis of the amp to the ground connection of the PC power supply (might not be the case!), carefully of course.  

post #3 of 25
Thread Starter 

No, power supply stayed the same. Essentially I took everything in one case and put it in another. Now the PSU I'm already a tad suspicious as when i booted my PC up without keyboard it complained that power supply surges were detected during previous bootup, although apparently this is a fault of the motherboard and nothing is wrong with the PSU. But this happened around the time a graphics card died from a bent HDMI pin and destroyed DVI port, so its difficult to know what caused these issues.

 

The amp is on the other side of the room so is difficult to connect a ground to the PC power supply.

Thanks anyway this gave me some other ideas, and I'm getting suspicious of this PSU now, but I can't find an old one to test with, (one that isn't entirely molex connectors xD)

post #4 of 25
Quote:
Originally Posted by GoldeneyeDS View Post

 

The amp is on the other side of the room so is difficult to connect a ground to the PC power supply.

This would be the problem.  Your amp MUST be connected to the same ground as the PC.  Run another ground wire from the amp chassis to the PC chassis and give it a try.

post #5 of 25
Thread Starter 

Ah okay, thanks!
What cable would work to connect the two chassis?
 

post #6 of 25
Quote:
Originally Posted by jaddie View Post

This would be the problem.  Your amp MUST be connected to the same ground as the PC.  Run another ground wire from the amp chassis to the PC chassis and give it a try.

This does not guarantee complete elimination of ground loop problems. I still had a ground loop noise (especially when my GPU was on load like in a game) even though everything was plugged into the same power bar. The only 100% way to eliminate it is to use optical output from PC to achieve complete galvanic isolation of your audio equipment from your PC, but of course that means getting an external DAC and accept optical input.

post #7 of 25
Quote:
Originally Posted by Jd007 View Post

This does not guarantee complete elimination of ground loop problems. I still had a ground loop noise (especially when my GPU was on load like in a game) even though everything was plugged into the same power bar. The only 100% way to eliminate it is to use optical output from PC to achieve complete galvanic isolation of your audio equipment from your PC, but of course that means getting an external DAC and accept optical input.

Not quite correct.  Proper grounding does, in fact, eliminate ground loop problems.  However, it's still possible to have noise in an analog connection to a PC because of poor power supply design. That's not a ground loop problem as such.  

 

Back to the OP, I'd first try moving the amp to the same location as the PC, and with short cables and powered from the same strip see if the noise goes away.  If it does, next connect it with just the long audio cable, see what happens.  If it's still quiet, then insert an extension cord between the power outlet where you eventually want the amp to the test location near the PC.  See what happens.  If that causes the problem, leave the extension cord in, but put the short audio cable back in. 

 

What you observe in these simple tests will determine the best solution.

post #8 of 25
Thread Starter 
Quote:
Originally Posted by Jd007 View Post

This does not guarantee complete elimination of ground loop problems. I still had a ground loop noise (especially when my GPU was on load like in a game) even though everything was plugged into the same power bar. The only 100% way to eliminate it is to use optical output from PC to achieve complete galvanic isolation of your audio equipment from your PC, but of course that means getting an external DAC and accept optical input.

 

While, yes, optical would in theory remove the ground loop between the devices, I'd have to buy an optical DAC, a longish optical cable, and a ADC, just to reduce noise that i only started getting recently. Its not a solution i want to go through until everything else has been tried.

 

Quote:
Originally Posted by jaddie View Post

 

Back to the OP, I'd first try moving the amp to the same location as the PC, and with short cables and powered from the same strip see if the noise goes away.  If it does, next connect it with just the long audio cable, see what happens.  If it's still quiet, then insert an extension cord between the power outlet where you eventually want the amp to the test location near the PC.  See what happens.  If that causes the problem, leave the extension cord in, but put the short audio cable back in. 

 

What you observe in these simple tests will determine the best solution.

 

With the first test, the noise is quieter. The ticking has gone, but there is still a noise. Seems less digital. Long audio cable same thing. When i put a extension cable between them the noise  is the same. Going to try connecting the chassis to each other, just looking for some speaker wire i can use. Thanks again!
 

post #9 of 25

I have the very same issue with my new Arcam irDAC connected via USB to the PC. The PC is grounded but so too is my amp which the DAC is connected to via RCA. So, I have this ground loop issue. There seems to be no way out. I would think all USB DACs would have this issue if connecting via USB. Completely ridiculous and I'm not moving to Optical either. I would be willing to go Coaxial but my soundcard does not support it. Such a nightmare.

post #10 of 25
Quote:
Originally Posted by Bloodflowerz View Post
 

I have the very same issue with my new Arcam irDAC connected via USB to the PC. The PC is grounded but so too is my amp which the DAC is connected to via RCA. So, I have this ground loop issue. There seems to be no way out. I would think all USB DACs would have this issue if connecting via USB. Completely ridiculous and I'm not moving to Optical either. I would be willing to go Coaxial but my soundcard does not support it. Such a nightmare.

The good thing is all USB DACs don't have this problem, it's the wall wart that come with the irDAC that the problem occurs. That PSU is not earthed and that's the drama, it allows the shell of the USB and the outer ring of the RCA to float creating havoc. 

If the amp, PC and DAC are plugged in to the wall or power strip at some distance apart, this further aggravates the problem.

 

Try these cheapest cures to begin with:

 - On the power strip, plug the PC in first after the cable enters the power strip, followed by the amplifier, and the DAC wall wart next.

 - Keep the USB cable short (less than 1m) and the interconnect to the amp short as well (1m or less),change RCA cables.

 - If you live in the USA, rotate the Wall wart 180deg in the wall socket, to tie the shell of the DC output to "earth via the neutral"

 - Tighten all the chassis screws on the PC, make sure the AC cable to the PC is not cracked, frayed or loose fitting.

 

More expensive options:

Replace the Wall wart PSU with a three prong 12V 1A (or more) DC power supply. You can build yourself if you are brave, the exotics can for $2k+, so careful.

Replace the DAC with a mains powered PSU inside type

Replace the PC's power supply, if you have a notebook, their brick power supplies get the clap after a few years and emit noise.

post #11 of 25
Quote:
Originally Posted by One and a half View Post
 

The good thing is all USB DACs don't have this problem, it's the wall wart that come with the irDAC that the problem occurs. That PSU is not earthed and that's the drama, it allows the shell of the USB and the outer ring of the RCA to float creating havoc. 

If the amp, PC and DAC are plugged in to the wall or power strip at some distance apart, this further aggravates the problem.

 

Try these cheapest cures to begin with:

 - On the power strip, plug the PC in first after the cable enters the power strip, followed by the amplifier, and the DAC wall wart next.

 - Keep the USB cable short (less than 1m) and the interconnect to the amp short as well (1m or less),change RCA cables.

 - If you live in the USA, rotate the Wall wart 180deg in the wall socket, to tie the shell of the DC output to "earth via the neutral"

 - Tighten all the chassis screws on the PC, make sure the AC cable to the PC is not cracked, frayed or loose fitting.

 

More expensive options:

Replace the Wall wart PSU with a three prong 12V 1A (or more) DC power supply. You can build yourself if you are brave, the exotics can for $2k+, so careful.

Replace the DAC with a mains powered PSU inside type

Replace the PC's power supply, if you have a notebook, their brick power supplies get the clap after a few years and emit noise.


Hello!

 

Many thanks for the great reply and help. A very interesting read!

 

I've been doing some more reading and apparently all Arcam had to do was implement a galvanic isolated USB input to eliminate noise and electrical interference from a ground loop situation. The Rega Dac has an isolated USB input so yes not all USB DACs have this issue; just a shame this £400 irDac has a non isolated USB input.:confused_face_2:

 

I tried what you suggested, plugging in the PC, amp and then Dac closest to the incoming cabling of the multi socket power cable. This did not work unfortunately.

 

I also tried replacing the RCA, no affect.

 

So, if I understand correct, all I need to do is get the irDac earthed and that will solve my issue? If so, could I buy this: http://www.russandrews.com/product-PowerPak-II-1801.htm   ;and then use an EU earthed power cable like this: http://i00.i.aliimg.com/img/pb/680/643/406/406643680_007.jpg

 

Regarding the PC's power supply, how can I buy one which will eliminate this issue and what do I look for in the spec? Anything specific?

 

Really appreciate the help here. Surely there must be others with this issue too. Arggghh.

post #12 of 25
Quote:
Originally Posted by Bloodflowerz View Post
 


Hello!

 

Many thanks for the great reply and help. A very interesting read!

 

I've been doing some more reading and apparently all Arcam had to do was implement a galvanic isolated USB input to eliminate noise and electrical interference from a ground loop situation. The Rega Dac has an isolated USB input so yes not all USB DACs have this issue; just a shame this £400 irDac has a non isolated USB input.:confused_face_2:

 

I tried what you suggested, plugging in the PC, amp and then Dac closest to the incoming cabling of the multi socket power cable. This did not work unfortunately.

 

I also tried replacing the RCA, no affect.

 

So, if I understand correct, all I need to do is get the irDac earthed and that will solve my issue? If so, could I buy this: http://www.russandrews.com/product-PowerPak-II-1801.htm   ;and then use an EU earthed power cable like this: http://i00.i.aliimg.com/img/pb/680/643/406/406643680_007.jpg

 

Regarding the PC's power supply, how can I buy one which will eliminate this issue and what do I look for in the spec? Anything specific?

 

Really appreciate the help here. Surely there must be others with this issue too. Arggghh.

 

There's a downside to isolated inputs on the USB. What it does is to create a barrier for the two differential wires as well as the +5V and 0V, so that's not so good. 99% of DACs say $1000 up don't bother as it does degrade the sound. 

 

The power supply looks good from Russ Andrews, match the output connector carefully with the irDAC so the two physically work.

Quiet PC power supplies are about, but with so many rules for EMC compliance, it's difficult to offer one. I didn't see you were running a PC and not a laptop until i reviews the reply.

 

Perhaps try a powered USB hub, any cheapie will do, you might get some attenuation of noise through between the PC and the DAC.

 

Another alternative, and you can keep this for a long time with any DAC you buy, is the iFi-USB, this gives the DAC a new clean 5V and it can also isolate the shell of the USB. Prices are USD200. iFi also make a DAC that looks the same if you're ready to throw the irDAC in the toilet.

post #13 of 25
Quote:
Originally Posted by Bloodflowerz View Post
 

I have the very same issue with my new Arcam irDAC connected via USB to the PC. The PC is grounded but so too is my amp which the DAC is connected to via RCA. So, I have this ground loop issue. There seems to be no way out. I would think all USB DACs would have this issue if connecting via USB. Completely ridiculous and I'm not moving to Optical either. I would be willing to go Coaxial but my soundcard does not support it. Such a nightmare.

 

Hi,

 

Do you hear ground loop through your headphones or is it just through your speakers? 

 

Take a look at this :

 

http://www.theworshipguitarist.com/blog/theworshipguitarist-experience/usb-ground-loop-noise-eliminated/


Edited by fluidz - 11/2/13 at 4:49pm
post #14 of 25
Quote:
Originally Posted by fluidz View Post
 

 

Hi,

 

Do you hear ground loop through your headphones or is it just through your speakers? 

 

Take a look at this :

 

http://www.theworshipguitarist.com/blog/theworshipguitarist-experience/usb-ground-loop-noise-eliminated/

The butcher guitarist, idea of the shield is to keep the noise out, there;s still a lousy grounding system happening on his AC lines.

post #15 of 25
Quote:
Originally Posted by fluidz View Post
 

 

Hi,

 

Do you hear ground loop through your headphones or is it just through your speakers? 

 

Take a look at this :

 

http://www.theworshipguitarist.com/blog/theworshipguitarist-experience/usb-ground-loop-noise-eliminated/


I hear the feedback/noise through the headphones. Even when I move my mouse I hear the noise in the headphones.

 

Thanks for the link. Now that is very interesting but I'm very reluctant to cut my USB cable , as tempting as it is. I'll consider this as a last resort if need be. Thanks!.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Computer Audio
Head-Fi.org › Forums › Equipment Forums › Computer Audio › USB DAC Suspected Ground Loop Issue