So yesterday I built this Polysynth by Albert Nystrom from his GitHub page. Schematic is totally out of whack and the code doesn’t compile initially untill you assemble it into some sort of order. But I digress. This morning I powered it up and tested it. After finding one wire out of place it worked but was wobbly, so I fixed the Pitchbend input and the preset selection which I don’t have wired up and it became more stable. Poly mode is a bit flaky and seemed to hang occasionally, maybe it’s too much for the T3.5. So now it’s working I’m just trying to tidy the code up and fix the mux routines so more analogue pins can be moved to the mux and free up a lot of the pins on the Teensy. This will save having to use the underneath pins for additional inputs.
So I added 3 more 4051 mux chips to the design and relocated all the analogue inputs onto these mux chips, everything working great. I updated the midi routines and this is now smoother and polyphonic mode works properly now, mono is a bit lumpy and could do with some note priority settings, but I’ll get to that later. I also moved the digital inputs around a little to free up the main SPI ports to attach an OLED screen to make saving and loading easier in the future. New schematics and code have been published to my GitHub page above.
I’ve added the patch memory from the other synths based on the Tsynth patch manager. You can now store 999 patches with names. I’m going to add functions over midi such as pgm change, pitchbend, modulation and aftertouch with destinations.
I’ve probably spent more time than I should have on this synth, but the VA software and integration of my programmer were giving me a hard time. But it’s nearly finished, just the back panel to drill and mount and some note priority software to write for the mono and unison modes. It’s a 6 note poly based on Albert Nystrom’s home made Polysynth and I’ve added a programmer for extra sounds, midi support of modulation, aftertouch and pitchbend.
So I gave the Teensy 3.5 too much to do. I altered the design again to put all front panel controls on the mux and get rid of the 17 individual digital inputs to the Teensy, after that it started holding notes randomly and the aftertouch was unreliable. So I rewrote the whole dam thing and fixed the setup menus that had been bothering me. Now it runs on a T3.6 and everything is smooth. Aftertouch works, midi modulation works, the setup menu means I can change parameters like midi channel and mod/pitch depth and store them. I also finished the rear connections now so it’s boxed up. Midi out now sends each control so it can be used as a sort of midi controller and recorded and played back from a daw. It’s actually quite a gun sounding synth.
It’s a 2U ABS rack that I can buy in Ukraine. I think it’s made by Gantz, but other people have asked and found them in Europe etc. They are not expensive, the 3U was around 25 euros.
I did a search and found this from new Zealand so it seems they are multicomp parts.
I come from guitar pedal/amp building so it’s so ingrained to go for metal enclosures that I can ground. Seems like that’s much less of a concern in the synth world, definitely makes the drilling easier…!
The problem with most rack units is that they are mild steel and heavy. And yes difficult to cut, even if they have an aluminium front panel it will be 3-4 mm thick for strength. These are easily drilled and can be trimmed with a Stanley knife, so I drill holes inside any square cutouts and then just trim back the plastic with a knife. Only downside is the front panel is not very adhesive and I use adhesive printed front panels, they need a layer of pritt stick on the panel before applying or they will peel off, a bit like 3d printed panels, not very adhesive due to the pores.
