After looking at the pictures of the ZSP1 it looks like the main
grounding path and signal ground are through the aluminum plate!

It seems that most of Steve's other designs use a dedicated signal
ground.  I was wondering if there was a way to wire the ZSP1 with
only one point where signal and ground are connected?  My other
worry is whether or not an aluminum plate is a sufficient conductor
for audio signals.

Chris