I have the RR2150 w/ USB "in" from a USB "out" on my 6-year old Dell Inspiron desk top computer.

When I first hooked up my system, I tried a USB out directly from the back of my computer. There was very perceptible digital backgound noise on the line, with and without program content.

I tried another USB port from a powered hub. The signal was much cleaner, but there is still a little background noise, but much less, perhaps 80% less than the first connection. I tried both with two different USB cables. The run is about six feet.

What trouble shooting sequence would you suggest?

Reroute the USB cable?

Add a choke on my USB cable? Type?

Get expensive USB cable? Brand?

Get a new sound card? (I understand the USB out bypasses the computer's sound card. Is this correct?)

New computer? How would I be sure this wouldn't still happen?

Separate dedicated digital player? Are these totally noise free?

Other?

Or should I expect a little bit of phssst, hsshssst, like low volume frying bacon in the background from any USB source?

I would suspect the pic at first. Can you borrow a laptop and try that. I use my 10 year old dell laptop as a music server with my 990 and it sounds great. The usb does bypass the sound card and puts the 990 days on stream.

Interesting experiment.

Let's say I am experiencing background noise of 3 on a scale of 1 to 10 through headphones played through my amp from my PC. Volume on the RR2150 set at 50%.

I unplugged the USB cable from my desktop computer and the noise drops to 0. I plugged the cable into my laptop and INITIALLY the noise is 1, but after 5 to 10 seconds increases to 2, slightly less than the desktop, but still there. I then plugged the cable back into my desktop and the noise starts at 1 (like initially from the laptop) and in 5 seconds goes back up to 3.

I notice when I move the wheel on my wireless mouse feeding to the desktop, I get an increase in noise as the wheel turns. I also notice when I plug the cable directly into a USB port on the computer that there is more noise (perhaps a 4) than when I have it plugged into the "Plugable USB 2.0 10-port hub" that is plugged directly into the computer. This is likely because the power supply of my computer is noisier than the independent power supply powering my USB hub.

So from this experiment I conclude the following:
* Some noise comes from my PC
* Some noise comes from the cable and/or my laptop.

Is there any fix for noise coming from a PC USB output?

I have ordered a package of clip on cable chokes to install onto my USB cable. I'll be trying that by Friday and let you know the results. Someone suggested getting a set big enough so that I can wrap the cable around it 2 or 3 times. Does anyone know anything about the science behind that?

My next step is to spring for better cable.

Does the noise change if you wiggle the usb cable at either end.

No, the noise does not change if the cable is wiggled. It sounds like I either need a device that reduces (filters/masks) that noise from the USB jacks of the computer box, or I need a different source of music if I want to eliminate that background noise. There is a super hub called Vaunix hub that sells for $200 that is worth looking at - I have an inquiry into them asking if their device is designed for this type of noise elimination.

Obviously most desktop computers are not designed to be low noise music sources. I would like to find a way to overcome this reality short of getting a new computer or moving everything over to my slightly quieter laptop.

Just out of curiosity, are you locked in to using USB? Is there a reason you can't just use a good quality sound card and connect to the analog inputs?

Good question.

To directly answer your question, one of the reasons I bought the 2150 is because of its USB input - thinking I would get the best sound quality directly from my computer's innards. So I have been trying to make that approach work.

Isn't a computer sound card just another name for a DAC, aka digital/audio converter? I already have one - inside the Outlaw 2150. I don't understand what advantage a new "sound card", aka "DAC" would provide.

What has been people's experience with a good quality sound card compared to using the USB out to the Outlaw 2150? And how much does an upgrade quality sound card have to cost to make a noticeable difference, especially in getting rid of my existing USB digital garble?

I have to admit that 95% of the music I listen to masks the low level garble. It is primarily noticeable when there is no signal present. I guess I was expecting total quiet which I do experience when I play my Kindle Fire HDX from its headphone out jack into the 9150's front panel input - total quiet, even using a cheap cable.

Would an EXTERNAL sound card work as well as an internal? I guess it would still be subject to the same USB input noise that I am experiencing now. I don't understand how a new sound card would help. Please explain.

Will either approach (internal or external sound card) eliminate the background USB garble? Or will it become background analog sound card garble?

I don't think adding a ferrite to the cable will do much as their purpose is to clean up high frequency interference and it sounds like your problem is power supply noise. However it's an inexpensive thing to try so I'd say go for it.

Other forums have been talking about this:

USB Buffer

that they say cleans up the noise on the USB power line.

I've never heard of this company or their products, but given that the Wyrd is pretty inexpensive and they have a 15 day return policy (with 15% restocking fee) it might be worth looking in to.

Good luck.

I wonder why I would need an isolator with a big power brick like the Wyrd. Would an isolator without an external power supply work when moving digital audio from the computer to the RR2150? The amp just needs the digital signal, it doesn't need 5 volts of power with it, does it? There are some for $40 that don't use external power like this one:
http://www.amazon.com/HifimeDIY-Isolator-ADUM4160-signal-isolation/dp/B00F4SCCR2/ref=pd_cp_pc_0

What do you think?

The connection from your Kindle is analog to analog and may not be indicative of the health of the usb input. Have you tried the headphone out on your computer to the 2150. My money is that the pc is the issue.