Very interesting gear !
It's ananalogue delay unit based on SAD 1024 by Reticon and it's a really stereo unit.
I have a C4000 preamp with delay unit based on SAD 4096 , but it's mono with hi frequencies shifted .
Any way these systems are hard to adjust and ,expecially, the placement of rear speakers could be critic.
Have a good fan and do not exceed with the effects .
The secret is : the rear speakes must exist , but you must not hear them .
The delay unit is not Dolby Sorround or Dolby Digital .
Ciao
Marco