Category Archives: drum machine

Various updates

So a few things have happened in the two months that have passed since my last blog post.

I built a MIDIBox Seq V4. It doesn’t have a proper front panel yet, is just Wilba’s PCB mounted on a piece of acrylic. It is, however, functional and great as it is, so for the moment I’m crossing sequencing off my list. I’ve also got the parts for a MIDIbox FM synth which is polyphonic, so maybe I’ll have my first piece of open hardware music soon.

The sampler is progressing in various ways. A friend of mine is designing a board based on the STM32F4 with a few megabytes of external SRAM. It will be ready, hopefully, within a few months. This should be a good platform for a sampler, and also for effects which need more working memory than microcontrollers have on-chip.

Another interesting development is the port of the MIDIbox software to the STM32F4 Discovery board. This is a cheap development board based on the same Cortex M4F from ST that my friend is using for his board. The chip on this is faster than the LPC1769 used in the regular MIDIbox core, and has a number of instruction set extensions as well as hardware floating point that make it much more suitable for DSP tasks than the LPC1769.

The Discovery board also has an onboard audio rate DAC that the MIDIbox software can address, so it’s already a good platform for making synthesizers if you can tolerate C. As mentioned previously, there’s already a SD card based sample player that could provide a starting point for a proper sampler. This is my summer project. It’s not the variable-clock, 12-bit S900 recreation I really want to see, but it would certainly be useful for certain things, like a PCM drum machine.

Speaking of drum machines, I was pleased to see the Sonic Potions LXR drum machine sell out the first 100 kits in hours. This community is doing great things, and I look forward to seeing the developments.

Sonic Potions Drum Machine

A fellow named Julian is making a virtual analogue/FM drum machine with built-in sequencer. The details are over at It looks quite exciting, all open hardware and software. Kits will be available, although the mainboards containing the main microcontroller and audio codecs will come preassembled as they’re smallish SMD components.

Incidentally, it’s based on the same STM4F chip that I just got a development board for. Mine’s yet to make a sound, though, but I’m looking forward to seeing the code and designs for this. And probably snagging a kit!