Whine/Hum Coming From Computer/DAC

[audioxtremist]

I recently purchased a Moon 300D DAC. First off, excellent DAC, definitely recommend it. My current setup is as follows:

 

Asus Xonar Essence STX > Moon 300D DAC via Coax > Moon i5.3 Integrated > Paradigm Studio 60s

 

The problem is when the coax is plugged in I get whine/hum at high volume. If I use TOSLINK optical instead, everything is great, very little hum at high volume. I get whine/hum with USB also, but USB is not recommended connection anyways (as said by Moon themselves! (for this particular DAC only)). You may ask, then why not use optical? Well, I find the audio quality is noticeably inferior in my case, my geuss is the sound card's optical converter isn't as good as its coax. So I'm stuck with Coax. How can I get rid of this hum? Everything is plugged into the same power bar. I've tried plugging things into separate outlets, didn't help. Ideas?

 

[The Computer Audiophile]

Do you know if the Moon galvanically isolates the coaxial input? My guess is this input is not isolated thus very susceptible to noise from a computer. Same with the USB input. Optical breaks the link and results in no noise but lesser sound quality.

 

[audioxtremist]

I will contact Simaudio (the maker of Moon products) and find out if it is galvanically isolated. I couldn't find anything on their website indicating that it is.

 

So the question is, what is the lesser of the two evils, a slight hum/whine at high volume, or slightly lesser audio quality (from my initial listening impressions)? Does the hum cause any degradation of the sound quality or is it just a hum and if I can't hear it when playing music then it doesn't really affect quality?

 

[Part-Time Audiophile]

Is the whine a constant hum, or does it vary with volume? If the former, it's probably a ground loop -- try floating the ground on the DAC with a cheater plug. If the latter, try a different coax cable.

 

[audioxtremist]

Not exactly sure what you mean by vary with volume. If I turn down the volume then the whine goes away. It is only present when I turn up the volume to 3/4 or more. Also, it changes depending what the computer is doing. If the HDD is going then i hear different noises. Depending whats on the screen it can be slightly different too.

 

I tried changing the coax cable, didn't help. I don't have a cheater plug, I heard those are dangerous so I don't really want to try that. I did try unplugging everything else on the line and that didnt help. But basically the only thing that causes problems is having the computer connected to the DAC via coax or USB.

 

[Part-Time Audiophile]

But the whine is coming through the speakers? And not from the gear itself, right?

 

Do you have access to something like a HiFace or some other USB-S/PDIF converter? Or a different computer you could use as a source, even if it's only one file and you have to use USB?

 

[audioxtremist]

Yes, the whine is coming from the speakers, not the gear itself.

 

I don't have a HiFace, but I do have a USB soundcard which has COAX output that I could try. I'll give that a shot and let you know the results. If that fails I'll try putting the soundcard into another computer and see what that does.

 

[audioxtremist]

So I hooked up my old USB sound card, Creative Live! 24-bit External, which has SPDIF coax output. No more whine! I cranked the volume all the way up and there was nothing but silence. Perfect!

 

Now the question is where do I go to next? Obviously the Creative card is not good enough quality to match the rest of my system. Will a device like the HiFace have noise, or is it well isolated like my USB soundcard? Any other suggestions?

 

[Part-Time Audiophile]

The HiFace should probably be whine-free.

 

[audioxtremist]

Thanks for the help. It's a big relief to get this solved. Time to do more research and spend more money. This seems to be a theme in the audiophile hobby, lol.

 

[The Computer Audiophile]

Be careful using a hiFace as it's not galvanically isolated and has some other design issues that may not resolve your issue. Just a warning. Please demo it if you can.

 

[audioxtremist]

Thanks for the warning. Like I said, "Time to research...", and after reading your review on this site I noticed that you said it is not properly isolated. I will look further. I see you recommend the Halide Design Bridge. I will spend the money if it makes sense. My only hesitation is the lack of 176.4kHZ and 192kHZ sampling rate processing. Do you know of any good options that offer quad-rate sampling?

 

[audioxtremist]

So after using the Creative USB sound card for a while I decided to give the Asus Xonar Essence STX internal sound card another try. I finally found the source of the ground loop. In case anyone else has a similar problem, here is my setup and how i fixed it.

 

PC -> Sound card (Asus Xonar Essence STX) -> DAC via SPDIF Coax

-> Integrated Amp -> Speakers

 

All fine and good right? There's more:

PC -> A/V Receiver via HDMI -> Projector

 

Still fine, now for the problem connection:

A/V Receiver Front Channel RCA Pre-Outs -> Integrated Amp

 

This final connection was creating a ground loop through the PC. The solution isn't great, basically remove the A/V Rcvr -> Amp connection while listenting to PC music, and connect it and remove the PC -> DAC connection when listening to AV sources (Blu-Ray). Hope that helps others.

 

And the results? Superb sound. Now that I can use the internal sound card without ground hum, the internal sound card really trumps the USB sound card that I had. A lot more clarity, presence, and detail. Really enjoying the music again.