The Mini SSL4000 project(diy dbx vca)

[Evillamp]

So i really wanted the sound of a ssl 4000 in my homestudio but iam no fan of plugins and record only the analog way.So i had this idea of cloning a singel channel of the ssl4000,complete with diy dbx202s and micpreamp , dynamics etc.
So for the eq part i got hold of one of caseys 4000eq,the dynamics will be provided by a original ssl4000 dynamics card that i found for a good price.Everything else including the vca fader will be recreated (somewhat) faithfully by me

 

[Evillamp]

The mic preamp was easy enough to clone.with that done the biggest part to figure out is the vca channel fader.ive been doing a deep dive into the dbx202 that is used there.got pcbs made for a gold can and blackcan and so far its successfull with minimal distortions.iam gonna update this thread with pictures and schems for what iam working on

 

[tommia 2]

Thanks for doing this

 

[Evillamp]

So for the Channel Fader ,the large one, I did solder this together. Just finished it yesterday. We can ommit the buffer for the Pc input and go straight from the Wiper of the large fader trough a 10 ohm resistor into R25 for the computer return

 

[Evillamp]

for the Fader i bought a few Penny&Giles Faders. Couldnt get hold of any vca faders so i used 10k Linear PGF3210 faders. I found this page in the manual for the Stereo Vca and image control circuit. Iam gonna take a few parts out of this for the channel vca ,for example the Fader Law adjust trimmer VR5 sounds like a good addition .Besides that the vca channel circuit doesnt have much difference to the stereo and image control.

 

[Evillamp]

So heres my 202 goldcan prototype ,the trimmers are for getting the correct voltages and didnt really fit the footprint i selected.yeah i also finished the control circuit ,i gutted a ADT audio vca fader for it and installed the pgf .so attenuation and boost seems to work great ,only thing i dont get is the infinite attenuation on the bottom of the fader,maybe there is a switch inside the ssl fader for disconnection or something? But so far the basics work.i have the vca running on a very simple test harness with a input resistor and cap as well as an output opamp and the symmetri adjust

 

[Evillamp]

So i spend the last few days testing the vca scaling pcb. As i said ,i cant get it to completley go silent at the bottom of the fader.so fearing the worst (my diy goldcan is a fail?!?) i solderd up a 202x from some dbx 2150s i had. Aaand well my goldcan is not to blame.they seem to respond pretty similar to the control voltage ,with the diy goldcan being a bit more crunchy at times. So ig ive proven to myself that the goldcans work. Iam gonna build a mute switch into the channel (because i can xd) so i dont really mind if it doesnt go completley silent at the faders end.So yeah a whole lot of words for a simpel update on the vcas but iam happy to report that they perform incredibly well for being made in my bedroom xd