I've built a stereo prototype, using the circuitry devised on the first post. Its a stereo unit and I used ganged pots for input/output and pots for attack/release. hardwired stereo.
I should probably post some samples. But if I was to give my (probably unforgivably biased) impressions of the unit.
The attack and release sounds like an 1176. More color than 1176 though. Its does a great job of adding the tube color we all love tubes for. Makes things just sound better. During initial testing it was noticeable for me on acoustic guitar...Hard to explain, but it just seemed to balance the frequency spectrum. Making it sound bigger and better balanced.
Where you might want to use the GSSL on your mix buss when you have a really drum heavy mix. This seems like something you would use....for everything else!
Anyway Putnam knew what he was doing when he made the 176, PRR knows this stuff up and down and made a gem when he made his vari-mu.
but his always seemed to be intended as just kind of a compressor your could make from the spare parts in your junk box, which I love about it.
This version is trying to take it a step further into a more polished design, by just adding little things (friendly with +4 operation, input/output, regulated 1.5v bias for example) and hopefully in the process I don't mess anything up, or take away from either of the designs.
And it is sounding great!
I'm going to finalize the front panels designs with dan, and then its off to the Fab house for the PCBs. And because the majority of the design came so selflessly from this forum, I want to keep the goodwill going by offering it as inexpensive as I can.