Here's a pic of all 8 preamp cards with 4 balanced line driver card loaded. 

The headphone card gets warm , so I'm only running 1. 

The protection diodes on the rear of the preamp cards are in the way of the SMD electrolytic caps ( they moving over about 10mm )

They were added to protect the PG2500's against voltage rail error !

The next job is to code the +-5v rail monitoring on the MC and have all the channels immediately shut down if there is a

voltage rail deviation > 0.1V

The would have preferred there protection diodes to be on there too ! next revision I'll move them over 10mn so they are well

clear.

This is all part of learning how to build multi board designs ! 

The gap between the balanced line drivers and preamps is tight but ok.

you can see the analogue IO panel FPC connector just fits.

I'm thinking of stripping a lot of the 3d printed box away so it's just a frame and then

using aluminium panels to make up the sides and connector panels of the box.