I know a little history about the company and product line. I had my first hands-on encounter with a Vocal Stresser and SCAMP modular rack in 1980 when I signed on as the Chief at an ad agency that had a new 24 track MCI room. Milam Audio had supplied all the gear and installed it just before I began working there, and there was that one Vocal Stresser and a SCAMP rack with just a few gate modules.
I was really knocked out by the VS, and the SCAMP gates were usable. Soon thereafter, we chased, and won, the USA advertising account for ADR. A LOT of gear was added to the studio via tradeouts. We added a second Vocal Stresser, maxed out two SCAMP racks, and added six Compex "N" modules.
For the latter, I added some switching so they could be used as six standalones, or in conjunction with the Transdynamic Processor. That box was basically a "crossover" with low/mid/high filtering to drive the inputs of a compressor, with a recombiner to put everything back together with a peak limiter at the output. The intended market was FM broadcast, and two radio stations here had them in their on-air processing (but with the much-less-expensive Express compressors) in the mid 1980's. It was sort of an Orban tri-band on steroids since you had so much control over each band.
Here's a scan I did from the ad agency's brochure showing the room as it currently exists. In the sidecar, you can barely see the six Compex "N" modules at the top of the left rack section. Directly below in the left rack, and immediately to the right in the other rack are the two SCAMP frames. Beneath the left SCAMP rack is an ADR "voice over" compressor (analog auto-ducker). The chair is mostly blocking the view of the Vocal Stressers beneath the other SCAMP rack. http://www.brianroth.com/pix/gv.jpg
ADR went through several name variants. Originally, they were Audio Design (Recording), Ltd. They eventually dropped the () in the name. We suggested Audio+Design with a new logo which showed up on some later gear.
USA marketing was handled by Nigel Branwell and his wife, based in the Seattle area. Nigel and I became excellent friends, since the ad agency appointed me as the account executive! Pretty crazy for me, since I was a Gearslut, not a suit, but I could speak the lingo. I was the copywriter on all the A+D ads that ran in the US. Nigel and I could also "party hearty" when we got together at trade shows, etc. I believe he moved to AMS or Amek, but I learned awhile back he had died from a brain tumor. I now wish I had kept in contact after the A+D days.
As for the electronics itself, things like the Compex were 70's discrete designs, Class A circuitry with a British flair. Later gear (especially the newer SCAMP modules) used opamps. I will agree that some of their pots and switches weren't the best quality, but it's typically not too difficult to find modern replacements.
I am a HUGE fan of the Compex boxes...they have quite a load of features (since they are a compressor, limiter, expander, and gate all in-one) and a great sound. Of course, you can see a 1979 LA-2A reissue in the pic linked above and not visible are some 1176's and other gear (there's another stash in the "coffee table rack at the far left of the pic, with the drum synth sitting atop). Each box provides it's own sonic footprint. We tried to have a little bit of everything, and a lot of A+D gear.
I have a ton of service and sales lit (imagine that!) in my files if anyone needs additional info.