Thanks, guys. The Revelation Audio Labs USB cable that @mike-marks and I have is a so-called “dual conduit” cable, i.e., it is built like a Y, with separate data and power conduits, or legs:
According to the RAL website, “the power leg may be required to begin the handshake between the DAC and the source, but once the USB driver has loaded, the power leg on these processors is no longer needed so you are free to entirely disconnect the power conduit. This means less noise from the PC or Mac, lower noise floor as a result.”*
*–While I think RAL makes fine cables, I cannot recommend buying factory-direct because of a reported history of lengthy delays between ordering and receiving product (I bought my RAL USB from a dealer who had the cable in stock). Sadly, this problem appears to be ongoing.
I am not familiar with JMaxwell USB cables, but I am intrigued and will check them out.