When I got my RxMx and FxdF, I reached out to Control to ask about the File. They only ever made 75 and said they didn’t sell well, though I guess they managed to sell out.
I asked if they would consider open sourcing it, but whoever I spoke to said that even open sourcing it wasn’t worth their time, and at any rate it would be up to the designer. Which, @Galapagoose, is that you by any chance? The Control File I did eventually track down was marked as a Whimsical Raps joint on the PCB.
I am guessing it would be a fairly easy circuit to make, since I believe it’s just the 6 dpo and FxdF outs running through DPST switches (maybe wrong switch type) and then the two “hidden” outs of the dpo made accessible to jacks. It’s passive. I considered giving it a go before finding a Control File on Reverb.