Hammond Scanner

I have been reading some interesting things about the rather freaky Hammond Scanner which was for production of vibrato on the Hammond Tone Wheel organs of the 50's & 60's. There is an excellent overview on the ModularSynthesis website. Whilst making one of those is reasonably impractical, despite having a lathe in the shed, I was also interested in the late Jurgen Haible's take on the idea here. I have done a bit of simulation of the important delay line and was also read some more from the ElectricDruid. Tom Wiltshire (the Electric Druid) suggests using all-pass phase shifters in Jurgen's design, this avoids the inductors which are expensive/bulky/prone to electrical pickup. In reality the Inductors look like the way to go. Simulation of all-pass filters shows quite a different response and the inductors aren't too onerous. I am thinking that the way to go with this is to build a board that has Jurgen's delay line but grafts on Oliver Gillets Frames style VCA's under Microprocessor control... It would work out to 4 off 2164 quad VCA's a couple of octal DAC's and a micro controller. Should be able to jam it all onto a Euro sized board as well for a laugh... May mock up a PCB and see how feasible it is...

Sdiarb

Bit of a long gap between posts... Sorry!

Have done this though:

It is a brutalized Braids Oscillator from Oliver Gillet. Oliver has put all the documentation/source code on GitHub under a Creative-Commons license -- which is fantastic... I have pulled all the code into a Keil project and twekaed it a bit to use some uController libraries that I wrote a while ago that are manufacturer agnostic -- i will plan to make a brother that is Tiva based with a different display...

Digital Frequency Counter 1960's Style

This is another project that is progressing agonizingly slowly... It is based upon a VERY old Digital Frequency Counter that was all old germanium transistors and small globes. I was going to try and to an authentic restoration but the globes had all corroded and kept falling off... There were also some sad things happening in the huge nest of transistors. I did find the schematic but really it was all a bit of a bridge-to-far. I have ended up making some small AVR boards and got some 5mm white LED's from Deal Extreme and it looks pretty original.

Limping back into life...

Doesn't look all that exciting but the Hellfire Modulator is slowly limping back to life. The old sticky panel has been peeled off -- quite a task! and the holes re-drilled for two of the pots with switches and the larger hole for the PWM range switch made smaller -- quite a task II! and now we are getting back to being able to where we should have been 3 years ago...

Asthetic has Knobs on....

This is a bit of an experiment in a number of ways. I have started on an 8 channel Envelope Generator that is based upon an enhanced DX7 style envelope control. I am also considering that really Forbin is going to be a bit big... I know that I am getting ancient and that large chicken head knobs are easy to see and that it all looks a bit Emerson circa 1974 but 40 years later I don't really have the space! Come what may the OctoEnvGen will be useful however it is packaged. It was a bit interesting to see though, how small a Euro synth actually is! I need to finds some knobs without markers on them though... These aren't pots but continuously rotating switches which control a TFT display which draws the waveform...

Cloudy

Well a bit more daydreaming and have been experimenting with a few ideas. I have always been fascinated by the MOTM 520 Cloud Generator VCO. It is a bit of an expensive beastie having an original price of $500 and no DIY option. That has become a bit easier with a DIY option for the E340 being offered but still $270 + postage and the $US Vs $AU is not in my favor at the moment... Anyway the aesthetic behind Forbin is not to spend much money, just to be unique and learn a bit so this represents my experiment with similar ideas. I have no real idea how they do it internally but I have prototyped up 4 sine wave oscillators with separate Brownian noise sources that modulate the 4 oscillators. The Brownian rate of change (well frequency I suppose -- Chaos Bandwidth in E340 parlance) and amount that it is tweaking each of the oscillators (Spread on E340) seem to all work fine. I want to make the number of oscillators also continuously variable rather than just stepped. I also need to do some thinking about a soft clipping arrangement Vs a an amplitude compression technique. I plan to rework this in Assembler after some of the prototype parts in C have been bashed out. The nice thing about the CortexM4F is that there are truckloads of floating point registers -- actually 32! so it is possible to leave a lot of the parameters in the CPU rather than loading them in and out of memory all the time... The sample frequency of this thing should be around ~150kHz to 200kHz so hopefully not too many artifacts will get through. It is pretty impressive what you can get out of a $7.99 evaluation board + a simple DAC!

Wavolver ii+

Made a PCB for Ian Fritz's Wavolver II but have made the Pulse Mix and the Fold Mix voltage controlled as well. I am now contemplating an 8 channel Envelope Generator to allow me to control all these elements at once... Haven't quite got it all going yet but certainly en'route to success...