The people who claim that USB cables for DAC don't make any sonic difference must be either ignorant or consider your wallet blessed. Well, they say digital is digital and 1 is a 1 and 0 and is 0, so how can a digital cable make a difference they ask. I was also a skeptic before and I didn't believe digital cables could make sonic differences. I am a computer and telecommunications engineer and I can tell you there is nothing as to a "digital cable" technically. A cable is a piece of wire (as somebody has said before, a coat hanger is also a piece of wire and it could serve as a speaker wire if you so wish.) and it is analog. It only acts as a "digital" cable when the connected systems operate in the digital domain.
I had always just robbed the USB harddrive cable for my DAC thinking why would I spend any money on cables since they don't make sonic differences anyway, until one day when I also need to use the cable for the USB harddrive, so I had to grab a different one from my cheap USB hub. Now I noticed my system's sound changed. I thought there was something wrong with my system or headphone, because it suddenly sounded so thin and lifeless. I couldn't believe it was the cable, but that was the only thing changed. So I waited until I finished using the USB harddrive, and I swapped the cheap cable out and replaced it back with the one from the harddrive. Voila. Things are back to normal. Digital is digital right? Wrong. Well some people may say placebo effect. But I doubt it. Since I didn't pay for either cable and wasn't expecting to hear a difference. But I did. So I eventually bought a $70 USB cable from an "audio" brand and was happy.
For the people who claim USB cables don't make any sonic differences I ask, have you tried them yourself? Are you speaking from personal experiences or just some myths you believe?
But when you transfer a file with a USB harddrive or USB hub via its cheap cable you never run into corrupted data you ask. Yes, it's true because the OS (Windows, or Mac OS, or Linux) layer handles the file transfer with CRC data checks, parity checks, error correction and retransmission built in. USB audio to a DAC has no such robustness. It's straight data streaming with no opportunity whatsoever for lost data retransmission or correction. Some better DACs have independent clocks with buffers that de-jitters the incoming signal. It's all in the design of different DACs. Also, some DACs draw power directly from USB and the quality of the cable will have direct impact on sound quality because its analog stage will be at the mercy of how clean the power rails are from upstream. Cables with better insulation to outside interference (yes even for "digital cables") will likely sound better.
Now I am not saying you should go and buy a $1,200 USB cable for your $100 DAC. There are USB cables that cost much more but I think the money should be better spent on other equipment that makes more improvement. However, USB cables are important and your system is only as good as the weakest link. Don't let a crappy USB cable limit the potential of your system which you spent so much money to build.
