A Squeezebox or Sound bridge are digital music controllers of sorts, somewhat similar in function to the traditional analog radio tuner.
However, they take digital signals in from multiple digital sources, generally over a wired or wireless (WiFi) network connection, the same as how laptop computers say connect wirelessly to a WiFi network and also the Internet.
Common sources of digital music that they connect to are various Internet based music or radio sources and digital music servers that might run on a laptop say in your home.
These devices also have an onboard DAC, though they are not as good as various outboard DACs available at reasonable cost today, so I would suggest that an audiophile will want to use these with an external DAC. They connect to the external DAC using the same kinds of wires typically used to connect CD transport or clock device to DAC. The DAC then connects to the pre-amp analaog line level inputs in the same way as would a conventional CD player.
See my system listing for an example of how this can work to deliver top notch sound on an otherwise conventional 2 channel rig. I use the Roku Soundbridge specifically in my system.
