[Schizeophonic]

I need some help here trying to isolate what I suspect is noise coming from my computer's USB bus. Additionally, since this pertains to a bottlehead crack, I will be posting there as well - but I already know, love, and have a username established here... so here goes.
 
I am currently hearing audible hum, swishy, bleeeeeeply sound in my setup, connected as follows:
 
a.) Desktop Computer USB ----> NuForce Icon HD ----> Crack ----> Senn 650s
 
Noise is independent of volume knob on crack and exists with gain at 0.
 
However, no noise is present if I do the following combinations:
 
b.) Chromebook or Laptop ---> NuForce Icon HD ----> Crack ----> Senn 650s
c.) Desktop Computer USB ----> NuForce Icon HD ----> Headphone Out Icon HD ----> Senn 650s
d.) Desktop Computer USB ----> NuForce Icon HD ----> RCA out Icon HD ----> Harmon Kardon Reciever ----> Speakers
 
I have tried different outlets - but I can't find a combination that works without noise for setup A.
 
Why would the setup work without the crack in the chain for the desktop BUT with the crack in the chain on a different computer?
 
I want to suspect the the computer's power supply, but the computer works in C and D with no noise. I don't believe the crack is the issue because it works just fine with 2 other PCs. This leaves me with big questions???
 
Does anyone have any helpful hints? I have crawled both the bottlehead forums and headfi forums to no avail. Right now, I can't think of anything else to do aside from randomly spending money on potential solutions and hoping they work. It's driving me nuts!
 
Thanks in advance for any help! 

 

[A_Man_Eating_Duck]

Do you have a powered USB hub that you could test with (e.g. monitor that has a usb hub)?

Desktop Computer USB ----> powered usb hub ----> NuForce Icon HD ----> Crack ----> Senn 650s

 

[Schizeophonic]

I don't have one handy - but for my own sanity, I could order one - they ARE handy. Additionally, in my frustration - I ordered a schiit wyrd through amazon via prime. Should be here Thursday.
 
Would a powered USB avoid taxing the power supply in the PC? I have been reading that galvanic isolation is the only way to travel, but I am unsure if I need to go defcom 5 super neurotic yet and spend all that moolah. Could a usb hub like the one below do the trick?
 
http://www.amazon.com/AmazonBasics-Port-USB-power-adapter/dp/B00DQFGJR4/ref=sr_1_2?s=pc&ie=UTF8&qid=1420583228&sr=1-2&keywords=usb+hub
 
I will check my monitors for USB ports as well - haven't really ever looked there.

 

[cdsa35000]

I sttill suspect groundloop from the PC powersupply and Crack powersupply.
Your other 2 PC's are laptops those DC adapters mostly don't pass the earth groundline through the DC plug.
Desktop's metal case and thus USB shielding is also directly connected to the powersupply's earth groundline.

Test these out for noise:
1) Desktop Computer USB ----> NuForce Icon HD ----> RCA out Icon HD ----> Harmon Kardon Reciever ----> Senn 650s
2) Desktop Computer USB ----> NuForce Icon HD ----> RCA out Icon HD ----> Harmon Kardon Reciever ---->RCA (Tape) out ----> Crack ----> Senn 650s
---
1) If iyou can't hear hum then there's no groundloop.
2) If you can hear hum then Crack cause the groundloop through the usb shielding.
---
Possible solutions:
a) The USB Cable Shielding is also grounded to PC= double ground =causing (datastream) groundloop noises!
Solution= Cut at only 1 side the USB Shielding wire/mess of the USB Cable.
b) If a) doesn't help than cut the usb ground wire pin 4 too..

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

http://www.head-fi.org/t/686609/usb-cable-cutting-ground-black-wire-to-eliminate-noise-between-computer-and-dac-solved

http://www.head-fi.org/t/745220/help-humming-noise

 

[Schizeophonic]

Additionally, I didn't mentioned that I have been running both laptops off their built in batteries. No DC connection - but I think that only makes the power supply to the USB on the desktop more suspect.
 
Thanks for that information! Before I start cutting cables, I am going to try the Schiit Wyrd "decrapifier" that I will receive on Thursday. If that doesn't work, I will resort to cutting USB over the weekend.
 
Never had an issue with dirty USB.... I am now starting to understand some of the frustration with it's use in audio....

 

[Schizeophonic]

Update - received Schiit Wyrd USB decrapifier. It cut noise down by about 80 percent. I still have a bit of high pitched whine.
 
Also, it looks like the lenovo desktop that I am using uses a special proprietary 14 pin power connector to the motherboard, which will make installing another power supply a bit harder. I rarely buy pre built PCs, and this just solidifies that I am not going to be doing that anymore.
 
So - I may be going the route of getting a sound card that outputs optical to get all things away from using the crappy power from the PC. This will eliminate the noise correct?
 
Trying out powered usb hub as well - I don't anticipate too much difference though using that instead of the wyrd - but who knows.

 

[Schizeophonic]

Problem resolved - I wanted to update the forums in case someone else like me decided to search for a solution to a similar problem.
 
Solution - installed a sound card that provides optical out to a FIIO E17 connected to an E09k. This eliminated all noise except a very slight high pitched whine. Replaced the 6080 RCA tube with a Chatham 6AS7G and it's dead silent (and it sounds better to boot. Win Win).
 
DONE! Thanks everyone for the input!

 

[vertical]

Thx for circling around and updating us with your solution.