Yes USB ports are noisy, thats where getting a better USB cable benefits, to send a cleaner signal. There are $3,000 USB cables, are they better than a $50 dollar one? i dont know, but i sure wouldnt spend more than $140 on a USB cable... unless i won the lottery!You can try any USB cable, even a printer one. IT would be nice to do an A n B comparison to see how a regular one compares to an audio dedicated one.
As for using your DAC with another thing other than a pc it is possible. I dont use android devices but im sure it is also possible to do it with them. For instance, with an ipad, i can connect the camera connection kit that sends out 16bit/44.1kHz and bypasses the internal DAC, then plug it into a powered USB HUB and then to a DAC and BAM you got music. Im sure you can do it with your nexus 7, just make sure you can bypass the internal DAC and send out the digital signal to the DAC.
Hmm, I'd like to see if this works. As far as I know the Nexus 7 doesn't have a DAC. Hell, it doesn't even have a speaker as far as I'm concerned. All it does is make a horrible noise. An ipad is entirely different than an Android tablet, that's why I'd want to try it before purchasing somehow to see if it would even work.
You can try any USB cable, even a printer one. IT would be nice to do an A n B comparison to see how a regular one compares to an audio dedicated one.