Aristoteles Logic Synth Update #2: Oscillators

The next module on the path of Aristoteles, the 'lunetta-style' synth, is finished! It's the central part of the synthesis: Oscillators. 8 of them. So essentially one could patch all 8 oscs into the 8-channel mixer and have 8 voice polyphony. They will also serve as the unique pseudo-CV clocks for the other modules, which is the main concept of CMOS-based synthesizers. The brain in all this is the classic 40106 chip, which is actually a logic NOT-gate flipping on and off. Below is a quick demo.

The oscillators have the following functions, as seen on the image to the right: The first switch lets you choose if the osc should be constantly on or momentary, determined by the red button. This allows one to use the synth as a simple keyboard with a little willpower. Next switch allows you to add extra capacitance to the oscillator, thereby setting the frequency range. The middle position of the switch is actually an off-position so the oscillator runs on the "offset cap" which is too small at the moment, so the frequency is very high. I wanted to have this range-switch so I could go with a potentiometer value around 100K for the frequency knob. This makes it easier to tune it without too big steps, as one gets if running on 1M or something in that range. I chose to have the whole synth only producing square waves, to have it ultra lo-fi and simple. But I  thought it could be nice to at least have PWM for each osc though, so this is what we have below the freq pot.

 It's a simple diode technique for adjusting pulse width of the wave, but I discovered that it was actually an inverse PWM, for what I wanted. It was setting the lenght of the off-time, not the on-time, so the LED's would be constantly on, only turning off for a short time, so I used another 40106 to inverse the HIGH/LOW order. This is the reason for 3 of the chips in the design - 2 IC's for getting 8 oscs and another one plus the leftover gates from IC 2 to have the pulses inversed.

The LED's are switched on and off with the help of transistors, to minimize voltage drop on the outputs. All the outputs are grounded with 100K resistors as well to prevent frying the chip if you touch the banana jacks.

Here's my quick and dirty schematic drawn in MS paint :)
Feel free to use it for inspiration in your own designs.

Greeting Card Sampler Boxed

I finally got to finish up my project seen in this previous post: Voice Message Greeting Cards turned into Lo-Fi Sampler. It's the 'voice message recordable greeting card' I hacked into a small looper with playback speed bend, now in a neat little encasing I found in a thrift shop. I think it's a intercom from the 70's, quite nice.

The video shows the features which are: potentiometer for varying the playback speed, switch for selecting loop mode, red button on the side is for restarting the device, which re-triggers the message, switch for selecting between the inputs - electret mic or input jack, jack for sending output to an amplifier and in the bottom are two banana jacks which allows you to control the device with a vactrol or light sensor, or any other resistive sensor :)

I had a very nice day at the FabLab's Maker's Day in Copenhagen, where I held a small symposium and a koncert with my current setup. One of the guys from CEO Bendorama who also played, got a recording of my concert - which includes the Greeting Card Sampler. (Thanks John!)

Live concert in cold war dome bunker

This autumn, several empty or unused spaces in Aarhus were turned into cultural platforms, amongst them were a minor cold war dome bunker where artists from DIEM were invited to perform a handful of intimate concerts for a small crowd. The event collided perfectly with the finalizing of my MicroWaveSampler - so my setup consisted of that, my Microcassette Tape Delay and my Spring Reverb Module. I borrowed my brother's GoPro Cam to record the concert from my POV.

Concert program folder showing inside of the dome

I'd recorded a sample bank for the MWS from instruments and other acoustic sources in my studio (the same samples used in this track) which brought a strange shamanistic and mystical vibe into the bunker. The lower frequencies, mostly from the shaman's drum-samples, resonated quite a lot in the room which you can hear in the video.
I didn't bother to tame the spectrum, I knew the room would be quite unique with some heavy room modes so I chose to embrace this and get a natural communion going with the dome. Improvising was nice because it allowed me to adjust to the surroundings.

Snapshot of my setup

I brought my crappy behringer mixer to be able to control the signal path and mix between dry/wet. But basically the main sources were the (microwave)sampler and a simple contact-mic bass-guitar which were sent to the mixer and then sent via a 'send' channel to the Tape Delay, back into the mixer and via the other send channel to the spring reverb. The reverb has dry/wet control built in so I could control the amount of reverb - which was convenient at times as the spring started oscillating very easily. I enjoyed the concert a lot, and it was quite exciting to perform with this setup!