He didn't specify what interface he was using. Most computer audio interfaces these days can handle high-Z instrument inputs directly - a 1/4" input from the bass. They also have audio outputs, typically 1/4" also, and usually a dedicated headphone jack. So the signal path is bass to interface via 1/4" high-impedence audio, interface to computer via USB (or Thunderbolt/FireWire), signal processing/recording/mixing on the computer, then back out via USB audio out to the interface for conversion to 1/4" audio out and headphones. XLR doesn't *necessarily* come into play.