It’s been a while….

It’s been a while since I’ve posted. I’ve been busy with work and also with QiX (and getting to grips with Linux), but I’ve also been tinkering with a new project.

Originally called “picowave” it’s now called “Zira” in keeping with my naming convention of classic 80′s arcade games.

I’ll say in advance, this won’t be made into a kit as it stands, and it’s also far from finished.


  • 2 oscillators each with 59 waveforms and de-rez
  • 1 Sub oscillator (an octave below Oscillator 1)
  • Hard Sync (oscillator 2 to 1)
  • 2 ADSRs, one for VCA, one for VCF. Each with linear attack, and expo decay and release
  • 1 LFO, Sine, Saw, Square and Random, plus key sync and single shot modes.
  • Analogue 24dB/Oct VCF (Korg NJM2069)
  • Analogue VCA (Korg NJM2069)
  • 64 Patch memories
  • Various modulation routings (to be finished)

The use of the NJM2069 means I cannot make this into a kit or production unit, sorry (i had a couple of spares and wanted to see what could be done). If a suitably small, and simple, VCF design can be found, then I’ll consider making a kit.

There’s no Audio DAC, I went all “old school” and used an R2R ladder made with 0.1% resistors (A few pennies more than normal resistors) as I wanted to see how “simple” and cheap I could make the hardware.

With this as one of the main compromises it means you cannot seperately adjust the level of the two oscillators, you can have both off, oscillator 1 on, oscillator 2 on or both on.

Also, the CV DACs for controlling the filter are only 12 bit (Micro chip dual 12bit DACs), again the idea was to make this as cheap and simple as possible, so there’s no high resolution DACs or complex analogue summing of voltages.

In a way, it’s a much slimmed down Monowave, though it doesn’t have the beefy moog ladder, 256 waveforms, no analogue ADSRs, nor refinement in attention to detail for the audio path. Neither does it have the same 1Mhz sample rate, this is much lower, around 200Khz. Also I’m using a much lower number of samples per wave, 128 instead of 256, so it’s a bit more “harsh” than the Monowave.

A picture with it next to GorF, as you can see, it’s the same PCB size, 80mm x 100mm,

So, you can see it’s the same size and concept as GorF. It runs of a DC wallwart the same as GorF (anything 6 to 18V seems fine). It’s taken a lot of messing around to get the NJM2069 to work, and I’ve learned a lot about the chip and it’s use.

Here’s some sounds of the current version (v0.24) -

If you want to see more, come to Synth DIY UK 2010 as I’ll be showing it there, along with GorF.

One Response to “It’s been a while….”

  1. Jase M Says:

    Great to see more stuff from your site.

    I had almost hoped this was another kit until I saw the Korg chip. Too bad, it sounds like a neat project.