[chuck8403]

I am using an iMac (mid-2011). When I have the USB hooked up to my Schiit Bitfrost or my Schiit Modi (then to my Lyr), I hear a noise that sounds like water splashing. I disconnect the USB cable and the noise goes away. The noise can very with the movement of my mouse (Logitech USB transmitter).
 
Once I decided to use the Optical output, the sound is great. So the problem is solved. But it is frustrating that I can't use the USB for audio. Not sure it really matters, but frustrating. Any thoughts on what is causing this? Just curious.

 

[precabal]

I've had similar problems on my macbook pro, using another DAC (GeekOut), which are improved when changing to a more free USB port (sometimes the hub is shared with the mouse/trackpad, built in camera, etc), or sometimes by unplugging the power charger. Have you tried those?

 

[chuck8403]

Thanks precabal. It's frustrating. I took everything off of the USB hub on the iMac and the noise was still there. I used a Schiit Wyrd, and the noise is still there. Not sure what is causing it. May be the power. I need to look at that.

 

[bloster]

UHFmag.com, the site for one terrific audio magazine, has their last issue with an in depth explanation of computer audio.Issue 95 is the one to check out --go to "reading room" on the site. I promise you all your questions are answered there.

 

[zxathlon]

Have you tried all the USB ports on your iMAC?
Also you can try another USB cable.

 

[StanD]

You might have a ground loop.

 

[chuck8403]

I have tried a few different cables and each of the USB ports. Same sound. Through the Optical it is clean. Ground loop may be the issue. Not sure how to troubleshoot that.

 

[cdsa35000]

Its a common USB Groundloop problem, either cut the USB shielding and/or lift the power ground from the powersupply:
http://www.head-fi.org/t/751709/crackle-through-usb-audio-devices-when-plugged-in-to-external-power
---
If you can't DIY then buy Shiit WYRD to waste money?:
http://schiit.com/products/wyrd

 

[StanD]

You can also try plugging in all of your devices in the audio chain into the same power strip.

 

[chuck8403]

Ok, I have tried the Schiit Wyrd and all are plugged into the same powerstrip. Next step is to get a battery backup with a conditioner. We will see if that works. So frustrating. lol.

 

[cdsa35000]

First try cut off USB cable shielding as mentioned in those threads?
-Modi use USB power and doesn't have own powersupply, so if its same noise as Bifrost on own powersupply then USB shielding CUT need to be done and tested!

If wyrd doesn't work or change anything is waste of money like i told u so, than something else causing problem.

What USB soundcard is it?
Is there headphone/speaker out from the USB Soundcard and Do you hear noises?


Test without any other usb mouse etc. connected except usb sound?
Test with a laptop on battery?

Try plugged NOT into same powerstrip?
---
Ref:
http://www.head-fi.org/t/745220/help-humming-noise

http://www.head-fi.org/t/110528/noise-when-moving-mouse-hdsp-9632/45#post_11241010

http://www.head-fi.org/t/719506/buzz-hum-with-new-nuforce-icon-dac-and-akg-k550

 

[DDF]

It's a ground loop. Buy an olimex USB isolator, they're amazing. I had the same issue, this fixed it and the sound quality improved immensely

 

[StanD]

Like I said a bunch of posts ago, it's most likely a ground loop. Here's a link to another USB isolator. These gadgets do not connect grounds between the ports of the isolator. The Schiit Wyrd does not do this. Also as another poster said, try using just the headphone out of your source to listen for noise.
http://www.amazon.com/HifimeDIY-Isolator-ADUM4160-signal-isolation/dp/B00F4SCCR2

 

[chuck8403]

Thanks for all of the advice. I would assume since there is no noise coming from the optical output, the iMac is good. I think it is something in the USB. I will continue until I figure this out!

 

[Gr8Desire]

Every Schiit device I have connected to my mid 2010 iMac has a ground loop issue. All the regular tricks like plugging into same wall socket have not worked. The only exception is the cheap Schiit Vali and Modi. They have isolated DC wall adapters.

Hate say it, but I think it is Schiit's fault. No other device I have tried have this problem with my iMac. I even returned my Lyr 2 amp partly because of ground loops.