Several things distinguish the PRE550A from other digital/analog preamps. It is possible to turn off the digital section when playing an analogue source. The analog section has three inputs — one balanced (XLR), one unbalanced (RCA), and one video pass-through (RCA). There are two sets of RCA outputs and one set of XLRs.
There is a wide choice of digital inputs — I2 S (RJ45), AES/EBU (XLR), S/PDIF (TosLink, coaxial, BNC), and USB – plus there is a network input (RJ45) that accepts signals from a 10 or 100Mbps network. Built-in Apple AirPort Express support enables the PRE550A to work via a wireless AirPort Express network. It has a direct input for an Apple iPod or iPhone that bypasses the Apple’s internal DAC and uses only the PRE550A DAC. There’s also an S/PDIF output jack, should you want to send a digital signal to another component.
The asynchronous USB 2.0 connection for a computer requires a driver if you’re running Windows, but not with a Mac or Linux computer.