107 voltage Controlled Mixer

In a lot that I bought, I ended up with a PCB from a 107 Voltage Controlled Mixer and a 114 Touchplate Keyboard, shown below. I also have a 160 Noise Source panel that I haven't done anything with yet, but that's not important to this post. I ended up selling the 114 on ebay because I could not imagine making a panel and touchplates that would be convincing and anyway I don't really care for that module. However, I was fortunate enough to find a Buchla owner who had a 107 panel in their system, backwards, as a blank space filler. So I had both the panel and the PCB, I needed only to get the pots and jacks and wire it up.



Assembling this module was an easy enough task. Since the schematic is on the list of ones I WISH I had, I found myself asking around if anyone had this module and would take a picture of the inside and tracing out the PCB to make up my own schematic. Soon enough, I realized that the pots on the panel don't control the VCAs on each channel! They are actually input volume controls.That means that you can't open up a channel without sending external voltage. Totally weird. I guess that's par for the course with Buchla 100 modules.

After some reverse engineering of my PCB and a picture that I got of someone else's 107 guts, I came to realize this module is the equivalent of ten 110 gate modules tied to two output channels and those 2 then mixed. The nice thing about having a 110 VCA in a 200 system is that it has a much snappier attack than a 292 and allows you to cheat nature a little and make sharp percussive sounds. A 107 let's you do a whole drumkit like that!

As it turns out, the PCB was totally functional as soon as I wired it up. This system is coming together slowly but surely.