On the hardware front:

- Main boards of Rio and Dell are *identical*. Even the same ROM code. They work out whether they're a Dell or Rio by reading some diode straps on the front board.

- There was only ever one HW rev of the boards.

- The front boards *are* different, as are the LCDs (Dell and Rio LCDs are 180 degrees rotated compared to each other), but electrically the same, save for a diode or two used to identify the front board type.

It's possibly you just have a flaky unit, though. The PSUs have sometimes been known to go strange, though as the receiver has a 12v input (powers the amp directly) but runs from 3.3v via a maxim DC-DC, there's a lot of headroom for power fluctuations before there's a problem. There's a 5v analogue regulator too, which just drives the analogue side of the DAC, the headphone amp and the digital volume control.

Hugo