From what I recall it is a pretty big unit, so probably at least the width of a standard CD, although taller due to being a two box configuration.
You could probably get exact dimensions by calling or e-mailing Ray Samuels.
"Both, the amp chassis & the external power supply chassis, have identical width & depth but the hight is different.
Width, left to right, 12"
Depth, front to back 8"
Amp's hight, 1.75"
Power supply's hight, 2.5"
The hight of both chassis does not include the lenght of the spikes under each component.
The extension of the volume control is not included in the amp's depth."