Arduino control voltage quantizer

Heard about the Toppobrillo Quantimator over the weekend from a fellow modular nut, and wondered if I could write a quantiser from bits of the code and hardware from my still unfinished CSQ-100-ish sequencer project. So ta-da, here’s a demo.

It’s a bit annoying, but you get the idea – the Arduino is taking a random input (from an MFB Dual LFO) and forcing it to the selected key and scale on a trigger from a TR-606.  Hopefully you can tell that it’s displaying the key, scale, incoming CV value and output note value. When I flip the switch down, it stops accepting CV input and starts looping back over the last eight notes quantised.

It should be easy enough to expand the modes available. There’s a good list in this electro-music thread on building a PIC-based quantiser.

I used the second output of the MCP4922 DAC to provide a harmony part (the “h” value on the display), although it’s not attached to a oscillator in this demo. It’s tempting to add another DAC and have four outputs for chords, in the style of the Quantimator. IS FUN.

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DIY Polivoks filter fun

Polivoksfilter

This circuit board has been stuffed and sitting around for the last two or three years in a plastic bag, waiting for me to be arsed to wire it up to some power. It’s a clone of the filter in the legendary Russian synth, the Polivoks, by Marc Bareille. How does it sound? Well, with everything up to 11, pretty much like robots being eviscerated with a chainsaw.

So some slightly ropey demos: these are direct into my Audiofire 4 – first is the bandpass only, with a bit of envelope on the cut-off:

Lowpass only, env on cut-off, lots of resonance:

These are through a noisy spring reverb and BBD Korg Signal Delay, rather more listenable – as far as I remember these are mixing lowpass and bandpass:

Manually sweeping the cut-off, more crazy self-oscillation:

Sample and hold of noise into cut-off CV in, mental self-oscillation at the end:

Sample and hold noise controlling the cut-off, overdriving the filter, fiddling with the envelope on the VCA:

The patch chain is something like…

  • Analogue Systems RS95 oscillator pulse/square waveform
  • MFB VCA (to attenuate the osc)
  • Polivoks filter BP and LP out
  • Doepfer A138c mixer
  • Doepfer VCA out to mixer

Driving the RS95 is a Roland CSQ-100, which I love because of the step entry by keyboard. I’d love it even more if it saved sequences. It’s a such a basic thing, I’m surprised no-one has hacked up an Arduino version – I might get round to it myself, eventually. A CSQ-600 would be nice and that but they command vintage-enhanced prices these days – my 100 cost me twenty quid a few years back, the last 600 I saw went for £181. The nearest Eurorack-format sequencer inna CSQ style looks like the forthcoming Analogue Systems RS450.

While we’re at it, here’s a lovely drum loop from a big, sweaty man – sampled into an S950 at 10Khz, then back out through an Alesis Smashup on a lowish setting:

Here’s a couple of minutes dicking around with the Smashup output through the Polivoks in lowpass mode, increasing the gain to get the filter to distort somewhat – bass is rather flatuent:

And here’s the same business through the Polivoks bandpass filter, if you can take the excitement:

I’m regarding the fact that the thing works at all as a bleedin’ miracle, given my lack of electronics knowledge. The filter is running off the 12v supply in my Doepfer G9 case. Because it was seemingly designed to run off 15v, I changed a few of the resistance values as per this handy thread on electro-music, only I used 80k or so for R8 to get the cut-off range within human hearing range. Apparently R9 defines the cut-off offset – I stuck with 100k there.

I haven’t swapped the box caps for the bigger values, not sure what effect that’ll have, but I’ll give it a try. The resonance pot goes from tweeting sweetly to full on robot massacre in a tiny nudge, I’m not sure if there’s anything I can do about that. I’ve built it with the recommended ua776 in place.

Bareille himself recommends an attenuator on the input – initially I was using a spare VCA, which is a bit flash – strapping a 100k pot across the input worked too, increasing the range of sounds from mellow electrical farting to the usual lawnmowering-the-nuts-off-androids-style shrieks.

Next thing is more difficult, mounting it on a face panel. I’ve got a couple of Doepfer blanks to work on.

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