I really needed a good test bench for troubleshooting modules.. The only tool I've had so far has been a cheap multimeter, and that doesn't really cut it when it comes to calibrating V/oct or figuring out why some clock sources fail to trigger certain modules...
Essentially it's just a MFOS wall-wart dual power supply, a stripboard with some terminal blocks and headers for easy power hook-up, and a Xmega Xprotolab (a breadboard friendly 2ch oscilloscope, function generator and an 8ch logic analyser / protocol sniffer). The inputs of the oscilloscope are good for up to +/-30V, which is fine, since maximum voltage levels in my modular system is +/-12V. The function generator on the other hand outputs +/-2V (4Vpp), so it had to be amplified to allow for full CV range of 10Vpp.
Also mounted on the board are two potentiometers. One is for an adjustable CV output, the other for adjusting the gain of the function generator.
So, now I might finally be able to properly debug my modular... :)
All I/O-pins have headers for easy(?) patching of sounds, using little wires. Three LDRs can (with some tweaking and good luck) be used to pause the three clock-speed oscillators, or to bend their rate slightly. Also connected to the clock-speed oscillators are three LEDs, which can be used to either modulate the other oscillators, or to modulate other devices.
Melodies are generated by patching and setting the rates of the oscillators. Overall pitch is controlled with potentiometer. Glide is also sort of controllable. Certain connections with the PLL create sync and ring modulation effects.
Needless to say, it's very hard to use, doesn't play in tune and is overall pretty useless. But it's recycled leftovers, so it's all good...
This week I've built a couple new modules: 2 channel ribbon controller interface (position and force/velocity) with sample and hold, gate and trig out with variable glide and threshold. Multi Rescale 1 (or 2) input -> (2 or) 4 outputs, with variable level and offset for each output. Inspired by the Rescale module in Blok Modular. Super Psycho Modulation Source, by Ken Stone. Six square wave oscillators, switchable ranges and waveforms. Could be used for modulation, percussion and drones. Wavefolder with voltage controlled folding. Makes really nice FM-sounding timbres out of sine waves or twists CV's. Circuit from Yusynth. Battery Acid. I was looking for a circuit to build around two germanium diodes and found this little circuit. I didn't have any single opamps, so instead I used a dual and wired up the second buffer in some strange way (two red LED's were involved some way). That mod added some quirky, rectified, superdist, which might be useful sometime... I also added a switch to connect or disconnect the LED's and also a 10k pot to mix between two points in the circuit.
They're not 100% done yet, but are 100% functional...
I recently discovered the wonderful derivative works of Stanley Lunetta. After some time scouring the lunetta forum sub section of electro-music.com, I found two nice little schematics by Phobos. First was a dead simple x4046 PLL VCO. It has the distinctive feature of also beeing able to track pitch, as a PLL does.. It produces very nice, self-modulating sounds. Second schematic that caught my attention was the 4017-4051 melody generator. Basically it's a decade counter dividing frequencies, controlled by a multiplexer, which is controlled by the step count of the 4017 (iirc). Also incredibly simple: 1x 4017 decade counter, 1x 4051 multiplexer.
Right now, the oscillator section with 40106 is mounted on stripboard. It's connected to 3 leds and 3 ldrs in a modular fashion. The 4046 is yet to be integrated. I found some salvaged playstation buttons in a cardboard box. Could be used for gating four oscillators and keeping two oscillators in lfo-mode. 6 100k trimpots are also avaliable for some additional bending... Osc Pitch? Osc Level? Tri/Square mix? Hmmm... We'll see...
Another project completed! I started building on this case for my Shruthi about a year ago. The 3D-modelling and CNC-milling took about ~8 hours and 12 hours respectively, then it spent almost a year in a cardboard box for no reason... But now it's all sanded and shiny!
I added switches for selecting between two different logic chips, currently I'm using an AND-gate and an OR-gate (labels say NAND and NOR, but I didn't really see any point in inverting the outputs), and switches for cascading the output of one gate to the second input of the next gate.
All in all it seems to be working perfectly! Now I just need more clock sources :)
So I've been keeping myself busy during the last few weeks, building my very own modular synthesnajser! So far I've built all the PCB's from MFOS that I bought. and every single one works perfect!
In the rack at the moment I have: MFOS VC LFO, MFOS Dual AR-Generator, MFOS Dual Log/Lin VCA, MFOS Noise Cornucopia, MFOS 24dB LowPass VCF, MFOS State Variable VCF, MFOS 16-Step Sequencer and a semi-functioning MFOS SoundLab MiniSynth.
I've also built a passive splitter/attenuator (will be rebuilt to the active variant, with scaling and offset) and breadboarded a Quad Logic Gate (CGS design).
Next step is to build some kind of case for it. I have a few ideas that I'm working on. My goal is to make it both sturdy and lightweight enough for travelling.
Woke up at noon. Glanced outside. Noticed that the trees were all still. A day like any other. Special in some ways, the same in most other. This day was intented for fractals, mysteries and deep thought.