OK - sorted now.  Case on, all the screws done up and just it's now sitting nicely on the bottom shelf of my rack.  That blue LED is a bit bright  .

It's too late in the evening now to do any worthwhile testing but it works which is the main thing

Have noticed a snag though:  it's such a powerful amp (about 230W per channel into 8ohms - double into 4ohms :MILD: ) that it even when the volume control on my passive pre is at "mute" (which is actually just very high attenuation) I get significant volume coming through the speakers and the meaningful range of my volume control is now about 3 or 4 positions  .  It's made worse I because the DAC64 has a very high output and I'm using balanced connections all the way so there's an extra 6db there.

So - is there an easy way to attenuate the input to the amp without significantly affecting sound quality?  AFAIK Rothewell attenuators only exist in RCA form.  Is it as simple as sticking a resistor on the +ve wire?

Will give it a proper test tommorrow

Michael.