Many thanks, Zen. I will do the tests you mentioned.
Balanced connections are the standard: 1 ground 2 Phase 3 Rev Phase.
Connections between Hedd D/A and Ocl2 input is unbalanced, as unit demands.
DC, even with OCL2 bypassed, seems I get some considerable noise floor. I will measure everything and post 3 JPGS, before and after each module being engaged.
There were a couple of songs I had to do an eq automation to minimize the boring noise at the very end of a song: enabling LPFs.
The least noise figure is when (of course) everything is flat, no colour functions enabled ( from Ibis or Hedd) and OCL2 output gain is at Zero.
Greg commented something about adjusting internal trims, but if output gain is lowered, S/N will go too. SO, no cure in there...