Poly what? Yeah, I wasn’t really sure what to call this! In the final version of alfa4 I’m planning to normal lots of the inputs to outputs and there will be some sort of master controller. For the prototype, I haven’t done this as I want to work out what normalisations will be most useful first, and I wanted some way to control multiple voices at once, so a bank of faders that output a voltage seemed a good idea.
I put together a schematic – this is the first circuit I’ve actually designed from scratch myself without basing it on someone else’s design (though I did have a little advice via the Synth DIY Facebook group). It’s just a voltage regulator feeding +5V to a bank of 10 faders, with the output from each fader going through an op amp buffer and onto 4 jacks, which are just tied together like a passive mult – I’m not too concerned with a little voltage drop at this stage.
I laid out a stripboard design (I added the power to this as well, but I just did that on the board).
I’d also designed a panel for it. This version has labels on the faders, but I decided to omit these, as they can be used for anything!
The circuit was very quick and easy. You can see the power section in the image above.
I’d been dreading cutting the slots for the faders. Acrylic is a difficult material to work with and the slots in the middle were very hard to reach with my dremel using the little circular saw. I tried a few attachments, and resigned myself to the fact that it was going to look messy!
Still, the faders fit and slide smoothly!
The panel wiring was a lot neater! Quite proud of this actually.
Wired it all up and it’s working perfectly. Happy days.
I only have the second envelope module to go now, then that’s the prototype finished and I can start testing. In fact all the circuits for that are done already and I’ve made and wired the panel. I’m just waiting on a couple of 0.15uf caps then I can finish that one off. Exciting…