[Armaegis]

I've used ground loop isolators before (both in home and pro audio use) and have not noticed any degredation in sound. Granted I haven't A/B'd it, but I've never noticed any problems while doing my sound checks.
 
As for removing the usb device, it's really kind of a crapshoot on how to fix it. Buying a different device is no guarantee that the new one will behave better.
 
Getting an externally powered usb can sometimes alleviate the power issue, but that's assuming the power source for the hub is any better (at any rate, it will *maybe* provide more stable current overall when you have several devices drawing a lot of power). If it's a device noise issue, there's no guarantee that the noise won't work it's way through the hub back into the computer.
 
You also need to know how your usb ports are handled inside. Some computers may have multiple bus cards to handle all the usb ports (usually if you have a lot of them), while others only have one. Separating noisy devices onto a separate card might work.
 
Welcome to the happy fun world of computer audio

 
Really though, usb isn't a bad interface for audio. You might simply have bad luck. If you want to know pain, try hunting for ground loops in a PA system...

 

[Armaegis]

Oh here's another thing to try: get a cheap usb->optical converter* and use that to feed the TubeMagic. This disconnects you from the usb entirely. Some people don't like adding an extra piece in the chain, others think the optical is better, meh I say go with whatever works.
 
* I use a Turtle Beach Audio Advantage Micro II which cost me something like $25, and use that to feed my iBasso D10 (picked up the appropriate optical cable for maybe $5). The TBAAM2 also serves as an external soundcard in a pinch and has a ridiculously loud headphone out.

 

[brasewel]

I would definitely suggest getting a self powered USB hub and connecting your dac to it. That way it reduces chances of picking up interference from the computer.

 

[_Spanky_]

http://electronicsshop.dk/isoleret_usb.htm
'nuff said.

 

[tangelo]

Quote:

Oh here's another thing to try: get a cheap usb->optical converter* and use that to feed the TubeMagic.

 
Yes, I'm actually using one right now, the Turtle Beach Audio Advantage Micro. The pathway goes like computer>Turtle Beach>optical out>D1. I tried using both USB and optical, but noticed no difference in hiss/sound quality between the two. Since I had already bought the Turtle Beach and optical cable I figured I would use them. Does this mean that there is no ground loop present, and the problem is in the D1 itself?
 
 

 

[Armaegis]

Really? So here's what we've got:
- works fine when amping a Fuze
- noise on two different computers (one macbook, other pc?; noise is less on the macbook) fed from usb
- noise when fed from optical
- I assume you've tried unplugging other usb devices with no change correct?
 
So we can probably rule out a ground loop unless there's some wiring defect in the TubeMagic itself. I suspect it's the DAC portion of your TubeMagic that might be defective.
 
 

 

[Arctia]

Had the same problem with my computer. On my amp, my volume pot is marked from zero to thirteen
 
- When plugged into computer, I can start hearing noise with volume at 3.
- When plugged into laptop, I can start hearing noise with volume at 6.5.
- When plugged into Fuze, I can start hearing noise with volume at 12 (remember max is 13, so this is very good)
 
I was able to drastically improve the situation by using a noise-reducing surge protector, and a high quality PSU for my computer. The circuitry system in my apartment is pretty bad.
 
Currently I'm just using optical out to bypassed the whole noise issue. If you are still having problem with optical, then it's another issue altogether.

 

[tangelo]

Wait so, the main thing I still don't understand is how there is less hiss on the Macbook and zero hiss on the Fuze... a problem with the DAC could cause that? I always assumed it was something with the power since the Fuze and Macbook are more or less portable and my computer has a big ol' PSU with all these other miscellaneous peripherals. And if there was a problem with the DAC, how could I fix that? 
 
Arctia, was the noise issue before or after you started using optical/upgraded PSU/used noise-reducing surge protector? Also, are you saying that there is absolutely 0 hiss at all when using optical out?

 

[quigley0]

Can you confirm that your computer output is set to 100%? I had a hiss on my PeachTree Nova, but, it was because my computer output was only set to 50%. (also, i always set the computer audio output to be 100%, and whatever software i am using at 100%). that way i am just using the Nova for audio control

 

[JRG1990]

What about using shielded cables? , a sheilded usb cable is a must or stick a ferrite clamp on your current 1, also try a sheilded mains cable on your dac or a power conditioner.

 

[tangelo]

Yes, the output for all programs is at 100% (disabled volume control in Winamp since I would accidentally lower it sometimes).