I have been working on 8/10 channel mixer that would be the final stage between my diy synth and a typical commercial one. In the beginning I just wanted VC panning for each channel and gate input for muting but after looking at modular grid for some time I decided that it will have all the bells and whistles like input VCA for each channel with selectable responses between lin and log, panning with selectable responses, 2 aux sends, each with VCA’s (also with both responses available), UV meters, sub group and some other stuff.
After finalising my vision on paper I was left with 7 VCA’s per mono channel and 6 for stereo channel and that brought many problems - mainly how am I going to fit so many VCA’s under 5x20cm panel (dimensions of one channel) and how am I going to do this without burning hole in my wallet. There were a couple of options, firstly LM13700 and that was going to be my target but after a couple of days of simulating stuff in Falstad I realized that it would take too many IC’s and therefore space, and on top of that money. My second option was using something like AS3360/3330 but that would be 3 IC per channel and some OP AMPs for controlling them, and they would be more expensive (at least for where I’m located). My final choice was to use VCA design presented by Yusynth and change it a bit in order to get log response.
Here is the VCA, it uses 3/4 of TL074, 4 transistors and some resistors: https://tinyurl.com/26v37mlw
And here is VC panner based on that VCA: https://tinyurl.com/26tzrhh8
I haven’t build them yet, so I’m unsure if they would work in real life, but if someone could give me some feedback on them I would be really grateful