YASP (Yet Another Synth Project)

ok, ok, I know, I should finish something first…… but…. no seriously, let me explain….

So one of the things that frustrates me is having to sit in my study of an evening to play with my synths, it takes me away from my other half and my Suzi dog. Now my other half usually plays games on her laptop, or sometimes does some coding, so I figured why not make something I can have sat on the sofa next to me instead of needing my lab, power supplies, big screens, etc.

So I remembered I had this rather nice little Alchitry FPGA dev board, I found that someone had made a KiCAD library with the foot print and symbols for the connectors and I designed a couple of boards to fit in.

From left to right we have; 4 VCF/VCA analogue board with -5V inverter, STM32 board for storage and MIDI and the Alchitry AU FPGA board.

Each board is 65mm by 45mm, so pretty small which is neat. I can also power them all from USB C, so no bulky bench supply to carry with me. The quad VCF/VCA board has jumpers on the back, so in theory 4 of these can be stacked onto a single FPGA giving 16 voices. Now I don’t know if the FPGA has the “space” for that, but it has the IO to do it, so I figured why not 🙂

When they’re stacked they look like this;

Kinda cute eh?

The test pins on the side are for power and aren’t needed now the USB C power is working (I wanted to test the board on my bench supply before connecting it to my laptop and killing that).

and with the break out board on top, I can connect a USB logic analyser/scope and get access to the signals.

This all sits very neatly next to me on the sofa and takes almost no space. So now I can sit on the sofa with my partner and nerd 🙂

This isn’t a complete side step from Delta as it might seem at first, Delta uses FPGAs at it’s core, so a lot of what I do on here will go into Delta. The DACs are already proven and working, and they control the VCFs and VCAs perfectly. So I can focus on making the core of Delta on this little portable system.

At some point I’ll probably want ssome simple user interface for testing, I’m thinking something like a 2.4 or 2.8″ screen with rotary encoder and a few buttons, just enough so I can tweak parameters and check things work.

I don’t plan on making this a product, this is just for fun, and as I kind of challenge to see how small I could make a synth. I do need a name though, not sure what yet.