I am familiar with the 864 quirky behaviour, I have a Dizengoff D864 (mono) compressor, it was really cheap, the compression (the way it handles the gain reduction) is absolutely wonderfull, but I don't like the overall sound of this unit and I think that is due to component selection, especially the cheap transformers in this thing.
It's also slightly different from the original as I can't find the 10W 15K resistors in the Dizengoff ?
My thought was "this could be made better"
I always like to have some spare tubes for my gear, so at some point I ran into a batch of NOS 6sk7 real cheap, so I got a bunch of those old metal tubes.
Wich made me think "I could do a stereo version" and I found the schematics here... so I got going.
While doing some more research and getting my bits together I ran into a nice quad of NOS Sylvania 6sk7GT glass bottles, so I got those and tested them in my D864.... I was pretty wowed !
(They did over 20dB of gain reduction without acting funny, (in that circuit) they only fit with the top lid off wich was fine for testing)
Outputtube will also be NOS Sylvania 7n7's and got some glass bottles for the 6sq7 as well, I think these are NOS Tung Sol.
Trow in the Chicago output transformers and my Jorgen Schou input transformers, all polycarbonate caps in the audio path,.... I think I got a recipe for something really vibey.
I took your advice from CJ's 864 topic and went for 50K input pots instead of the 500K (I have both options) I also decided to make those lin instead of log as they track better.
I like the idea of stepped controls, (these things are expensive !) I allready put some stepped controls on the ouput as I found some really nice 11 step switches in my parts bin... I do have a bunch of enormous 4 wafer EBE switches from an old broadcast installation, but I doubt these will fit.
I have used DACT in my hifi tube preamp, these are really nice indeed but also quite expensive.
I've build most of this thing from old bits that I have been collecting (got for free) for years and I got a really nice deal on those ouput transformers, the meters and pushbuttons and tubesockets are from aliexpress, so I did not spend a lot of money on this, just invested a lot of time...
I'm not shure what this will bring me, I hope it will be sweet on stereobus doing 3-5 dB gain reduction max and glue the mix together in that sweet buttery vari-mu way, that only a real vari-mu can do.
Let's hope so