Once I received my Emotiva Mini Amp, to complete this chain, Computer > Dac > Amp > headphones, my expectations of sound quality wasn't as high as I hoped. After reading around looking for potential diy improvements I ended up cutting the 5v and Gnd wires on the Usb cable.
Cutting the 5v is supposed to help clean up the signal somewhat as it's coming from a noisy computer, and it did help - more on that later, however, I found after cutting the ground wire there was a sine wave noise leaking through the headphones, similar to ground loop noise, but didn't fluctuate at all, just one leveled beep. I tried switching between all usb ports, to no avail and tried lots of different combinations which didn't work. I wanted to find a way to remove the noise without having to patch the wires back up again. Cutting both wires in the Usb cable yielded improvements to the sound quality.
With both wires cut on the Usb, I found plugging my active studio monitors into the same outlet and turning them on made the sine wave noise disappear, how odd!, Leaving them switched off didn't help at all, they had to be plugged in and turned on. Not ideal if i'm going to be listening to my headphones for the remainder of the night.
In the end, I got fed up of leaving the speakers on just to clear up the sine wave noise. One thing is certainly clear, cutting the 5v and Gnd on the Usb made a huge difference in sound quality, I had done blind tests back and forth. But with the Gnd and 5v not sitting in the middle this sine wave noise was there, still intruding and obviously having an impact on the sound.
I found even though I disconnected both ground and 5v of the Usb cable as to Isolate the Dac from the Computer, I had not truly stopped all unwanted noise/distortion from travelling from the computer through the cable to the Dac, there was only two data wires connected! How can this be?
I started to fiddle with the Usb connection at the back, low and behold, with a slight tug as to not pull the wire completely out, the sine wave noise had gone!
My immediate thought was, once I try listening to some music the sound is going to be messed up, missing a channel or something, lol, nope, sound was clear as day, and my god it sounded much better than before, and before that.
I can't believe a £400 dac, async Usb n all, has been affected by the lack of galvanic isolation in such a huge way. To describe the difference would be easy.. Each sound has its own natural characteristic and is supposed have its own space so you can identify where it is, create a perfect picture, right? Well, out the box, using Usb, My M1 Dac couldn't provide an accurate detailed analogue reproduction of each sound, music was slightly blurry, lacked natural binding across the spectrum. Yes, at first I thought the sound was fab, or so I thought.
Now I have some sort of galvanic isolation working (Usb slightly pulled out), i'm shocked at how good everything sounds, especially 24/96 material, I didn't know my He-500 headphones could sound this good. I was missing out on detail, and now there is lots of it, lots of attack, energy and great synergy. Something the M1 dac is supposedly renowned for, but I never knew until just recently!
I blame the computer.
Just to clarify its not my imagination, If I plug that Usb cable all the way into the Usb port, the sine wave noise instantly reappears, of course, as mentioned above patching up the ground and 5v wires would eliminate the noise too yet defaults to mediocre quality.
I've been reading up on my motherboard, and found many have run into noise leakage issues with x58 chipset motherboards, something to do with cpu vaoltage leakage?? - I've tried disabling settings in the bios, to no avail.
For the time being my work is done. Will be looking into testing a Usb Isolator out in the near future so the Usb cable isn't half hanging out.
Update : My apologies for the amount of edits. Impulse writer.
Edited by fluidz - 11/17/13 at 7:43pm