We also picked some info about the Grampian 'Ambiophonic' Unit, Type 666. This is another interesting (and rare) piece of 60s gear: a version of the Type 636 designed to use the reverb "to alter apparent room acoustics" in auditoria. We've never had one in our hands and so can't report much more about it, but here is the documentation we have:
This page is part of our collection of resources on the legendary Grampian Type 636. Read more about this remarkable unit and see all the information we've gathered over the years here. We're fanatical about these units and sound they can produce if restored to full functioning - if you are looking for one of these units, or have one to sell in any condition, please get in touch.