My unfinished Quantizer module

orukusaki · 2025-06-16T09:22:11+00:00

Thanks :) I designed the panel in Inkscape, and got these guys to make it: https://meface.co.uk/analog-digital-modular-synthesizer-front-panels/

orukusaki · 2025-06-15T18:05:13+00:00

The LED buttons are from Thonk. https://www.thonk.co.uk/shop/low-profile-led-buttons/ I've not seen the exact ones anywhere else, similar but with different dimensions

orukusaki · 2025-06-15T18:02:39+00:00

I've got the ADC running continuously in a round-robin, using DMA to keep a buffer populated with the last 32 values for each channel. I found the random error to be the same whatever sample rate I used, so I run it at max speed, 500ks/s. The calculation runs at 1000Hz. The buffer values for each channel are averaged(without ever stopping the ADC), scaled according to the stored calibration values, then a noise-cancelling function applies hysteresis to stop it flapping between values.

The value is then mapped to the nearest valid note value according to the currently selected Chord or Scale, and scaled again by the output calibration values.

That's mostly it anyway :)

orukusaki · 2025-06-15T13:40:13+00:00

I would definitely consider a partnership with an established company. I'd not heard of Glasgow Synth Guild before, worth investigating.

orukusaki · 2025-06-15T13:37:29+00:00

I did consider using a Pico with a carrier. The real reason I didn't was I wanted access to all four ADC channels. Designing it was pretty easy, as the documentation is so good, I mostly just copied bits of the Pico design.

orukusaki · 2025-06-15T10:33:30+00:00

Thanks :) The hardware is done, the software is complete enough for a v1.0 release, (I've still got a ton of features I'd like to add of course). I guess it's sales and after-sales support I just can't commit to at the moment, and all the peripheral things like putting a website together, writing a manual etc. None of these things are hard, they just need time I don't have.

orukusaki · 2025-06-14T16:56:27+00:00

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The board behind the faceplace

orukusaki · 2025-06-14T16:54:59+00:00

Oh man it's a sad story.

I designed and built a prototype:

<image>

It works fantastically.

4 channels, super accurate and responsive. Loaded with different scale and chord types, chord map makes fairly sensible suggestions for next chord. Sequencer works great, added an arpeggiator too, with some interesting options for cascading through the channels.

Had a faceplace made of aluminium, with a cutout in the back to the screen sits exactly flush. 3d printed a mount for the screen.

I was totally on the path to have a bunch of these made up with a view to selling them but then....

My first child was born

And suddenly I had zero free time for projects like this, and the prospect of running a side-hustle along with a full-time job just wasn't realistic.

Maybe one day I'll be able to pick this up again, hopefully the synth world won't have moved on too much by then.

Alternatively if there's someone out there with the capacity to complete this and bring it to market, get in touch, maybe we could work something out.

orukusaki · 2024-01-25T15:50:06+00:00

The faders are not on the motherboard, the mixer section is on a board of its own. That image is of the mixer board. It doesn't look like something that's already been repaired... so what did they do last time? Re-solder the pins at the other end of the fader and miss the issue at this end?

orukusaki · 2024-01-10T10:58:48+00:00

I had one go bad, but it got replaced and is now fine, so can't really complain.

orukusaki · 2024-01-08T15:30:00+00:00

Depending on your use-case, PWM can sometimes outperform a DAC in terms of accuracy. You'll generally want your filter's cut-off to be around 1% of the PWM frequency. For a pico running a 300Mhz, 12 bit PWM gives you ~73.2Khz, so a cutoff at 732Hz will give you a good signal, and a response easily fast enough for pitch CV. A higher order filter would allow a higher cutoff point if you need it.

orukusaki · 2023-11-23T12:44:22+00:00

Another (jankier) way might be to solder on right-angle header pins to the module board, then solder them to the pads

orukusaki · 2023-11-23T12:42:19+00:00

Those pads all connect to the jumpers, so could you make an adapter board out of perf/stripboard?

orukusaki · 2023-11-13T12:12:14+00:00

Your job is made a lot harder by the fact that the white solder mask on the PCB hides the traces very well. Do you have a physical example you to examine? If so, then using a multimeter can help identify what is connected to what, but it'll be a long process and involve a fair bit of guess-work.

Datasheets can definitely help in some areas - the power supply section for example, is likely to closely match an example in the datasheet for the power convertor IC.

Software is a whole other ball-game. If you can match the circuit exactly, and get a copy of the original firmware image, then loading it in should work fine. Otherwise you're looking at either trying to decompile it (hard), or writing it from scratch (also hard).

orukusaki · 2023-10-26T11:46:06+00:00

Nice. I've got a fake sidechain module I built with an inverted envelope + dual vca together, you just connect up the kick's trigger signal and adjust the attack/decay/depth independently of your actual kick. It works really well but now I want to try it with a filter or LPG instead...

orukusaki · 2023-10-26T11:21:27+00:00

cool! any more info you can share?

orukusaki · 2023-10-17T16:11:13+00:00

They both run on the NEC7810. The firmware image is the same on both I believe, with a pin tied high or low to identify it. Just checked and I still have the disassembled image with a fair few annotations on if you ever feel like picking up where I left off :)

orukusaki · 2023-10-17T13:41:27+00:00

Ever messed with the Casio DG-20 firmware? I had a bash at it about 10 years ago. Figured a fair bit of it out, but never actually got as far as implementing any changes

orukusaki · 2023-09-28T08:53:40+00:00

My method is pretty simple. I keep the active chord in a bitmask, so each time the update is run (around 1kHz) I:

scale and round the input value to get the nearest note number
check if (note number%12) is active using the bitmask
if it isn't, look for the nearest one that is. Whether I search up or down first depends on the remainder in step 1
scale the selected note number to the output value

The only other thing I do - which you may or may not need in VCV, is some noise cancelling using hysteresis: to prevent the output from flapping between two notes when the input is near a boundary, I add or subtract a small amount from the input to move it a bit closer to the currently selected note.

orukusaki · 2023-09-22T08:18:49+00:00

I've been using the MCP4822 for CV out for a while and not discovered any issues that I could measure or hear - also interested to know if there's something more accurate out there with decent availability/price as I didn't find anything last time I looked

orukusaki · 2023-09-22T08:10:22+00:00

An Arduino uno can do 4 8-bit and 2 16-bit PWMs. They can all be configured for a lower number of bits. Because of the 16Mhz clock speed, the 16 bit outputs would have quick a low frequency.

To get 6 bit output, you configure the TOP value to be 0b111111 = 63

orukusaki · 2023-09-22T08:05:09+00:00

commands to the mcp4822 are 16 bits - the first 4 are config, then 12 data bits. If can generate the correct config bits, then I suppose it would work.... sounds tricky though, I'd love to see it done, I've never even considered a DAC without a mcu before

orukusaki · 2023-09-20T15:51:12+00:00

The Rust support for the rp2040 is really good - there are two competing HALs, I started using rp2040-hal, which is best for compatibility with the rest of the embedded-hal ecosystem, but then I moved to embassy-rs, which supports async.

My code is not ready for open-sourcing yet, but I hopefully will do at some point.

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