Used to own two stereo units. (I think the 'D' was stereo, and the "Q4" might have been a mono version).
Handy, quiet, -usable... Not thrilling.
Switchable high and low-pass filters, four bands of fully-parametric EQ also individually switchable if I recall correctly.
It's like a complete set of medium-priced tools. Great for problem solving, but not a 'character' piece.
-If your console has a fully-parametric 4-band EQ on every channel with swept, switchable high and low pass filtering, and you have plenty of channels, you might never patch it in (we had one in a Neve VR room and also another in an SSL room... and they were rarely explored). -But if you tend to run out of EQs, then these can do most problem-solving jobs competently.
Can't speak for how they stand the rigours of time, because ours were never rigourously deployed. -It may be that the pots become as scratchy as a mange-ridden dog after a few years; -I never had cause to open ours to se what typo of pots were used, but they felt as though they may not be Clarostats or some similarly durable brand... -That's just an impression though, no research was involved in the formation of that assumption.
For some odd reason, I thought of them the other day, and wondered if anyone else had ever heard of the brand...
-Keith