Need help understanding USB cables

Your DAC may be powered but its USB input / processor may need to be powered by the input device (i.e. USB streamer) 5v line. Having two separated / shielded wires, one for the data, one for the 5v power line, may benefit your DAC as it eliminates cross talk and other types of interference. Whether you can hear the difference by doing so or not, it's up to individual user / listener, system, etc.

Yeah, I also read that a USB cable that separates the two signals is best, which makes sense.  Some of them can be a bit pricey.  Ultimately I went with the LavryCable Ultimate Silver Dual USB cable that seems well made and obviously uses silver, and at $134 for a 1m cable I found it to be one of the more reasonably-priced options.  I can’t vouch for performance as this is the only such USB cable I’ve bought, but it doesn’t seem to be limiting performance in any overtly obvious way.  Hope this helps, and best of luck. 

+1 @thyname 

Going deeper down the rabbithole, a few manufacturers have two versions of a particular model, one with/without the power line. Those whose DAC doesn't need the power line sometimes report not having it lowers noise. Other cables have "dual heads", i.e. two separate USB connectors one has power and one has signal. Users who don't need power, just don't connect that lead to the DAC.

So a couple of cautions:

1) If you buy a "dual headed" cable and need the power line, may sure your gear can accommodate

2) If your DAC needs the power line be sure to get a cable that includes it. For example, my Denafrips DAC doesn't use the power line for playing music, but still needs it to complete the "handshake" which gets the DAC to lock on the incoming signal. A cable lacking power line won't work with it.

Cheers,

Spencer

You can test easily to see if your DAC requires the 5V power from the USB cable. You can block the 5V line (pin one) of the USB A plug with a small piece of card stock. The system will either work or not. If it works then the construction of the cable (regarding the power line) doesn’t really matter.

The required handshaking is done by the ground line, pin 4. That must always be connected, at least for a moment upon turn-on.

Thank you everyone, much appreciated!