During the internet outage we experienced for three weeks I was able to complete this entire project. It will need at least two posts to get up to date. In this post I’ll talk about each module in detail: the panel design, circuit changes, special challenges, etc.

Kareishuu VCO

The Kareishuu VCO is a standard modular oscillator with one special feature, an internal VCA to control the depth of the AC-coupled linear FM. No less than four panel pots are dedicated to it.

The FM input is a yellow jack indicating a signal input. There’s an associated attenuator. This signal is mixed with the oscillator’s own sine wave using the Self Mod pot. This mix is sent through a VCA with initial level FM Gain pot and an external CV, FM CV in. The other four pots are the standard Frequency, Frequency CV, initial Pulse Width, and PWM depth. All the features of this VCO are present. Two of these modules are included on the big panel.

Not A VCO

I Can’t Believe It’s Not a VCO is a filter that can oscillate.

The input is labelled VCF on the Eurorack panel and uses a jack normal switch to send a feedback signal to the input when not patched. For this banana version I simply added the feedback signal to the panel as FB Out, which is easily patched to the input for oscillator mode. In oscillator mode the Envelope and Gate inputs come into play, gating or enveloping the oscillator on and off. So it’s like a combination VCO, Envelope Generator, and VCA in this mode. The Response parameter (red knob) affects the shape of the envelope. If an external signal is patched to the input, then it becomes a filter with manual resonance. The main Out is the bandpass output through a distortion circuit.

Dual LFO/VCO

I greatly simplified the panel features for the Dual LFO/VCO.

The Eurorack panel supports the Sync and Step features that I decided to omit. I really didn’t need them, and both are implemented with the same IC. The parts count fell a lot! What’s left is a pair of very useful LFOs with a range switch that can take it into VCO territory. Sine, triangle, and square waves are simultaneous available for both. Frequency and Frequency CV pots complete the panel. I used this module for testing the other modules, as I went along.

Stochaos

The name Stochaos indicates a combination of Stochastic (i.e. Noise) and Chaos.

I slightly compressed the vertical spacing on Stochaos to fit eight banana jacks. I had to lose two outputs from the Eurorack version, but it’s not a big loss. Send it a clock and an optional reset and you get eight random gates and three CV outputs. I labelled the three stepped outputs Out 1, 2, 3, because I reserved the label CV for CV inputs to avoid confusion. (Outputs are green and CV inputs are blue on this panel, so there really isn’t any confusion!) As a bonus, Stochaos brings out a Noise (Pink on the Eurorack panel) and a Chaos signal for external use. These have orange jacks.

Helvetica Scenario, i.e. Dual S&H

Again I simplified the features for the Helvetica Scenario.

The Eurorack panel includes a VC Slewing feature and an LED for each S&H. I replaced the VC slew with a manual slew (red knob). I also added Chaos outputs for external use (orange jacks). Each side can generate two separate stepped CVs. It’s really convenient to just patch a Trigger input and get a random stepped voltage from the Stepped output. Slewing is applied manually to the main Output, for which an input signal is needed to sample from.

Flip Flop Chaos

Flip Flop Chaos is a weird module.

All the panel features are present, though rearranged from the Eurorack panel. Feed this a Gate (clock) and maybe some CV and strange things happen on the outputs. The Trigger output seems to go even without a gate in. When I first checked it out, the CV outputs were full of parasitic oscillations. I tamed them by adding some capacitors. I’ll say more about the assembly in the next post. The four LEDs are arranged in a square with their positions matching up with the red gate and trigger outputs.

Squid Axon

Squid Axon is a four stage analog shift register with feedback.

All original panel features are here, plus two additional attenuators. The three inputs are all mixed together and transferred sequentially to Outs 1-4 on the receipt of a rising gate (clock). The red Feedback knob is the non-linear feedback path. Linear feedback paths are easily self-patched from any output to any input. Banana jacks facilitate multiples in place!

Beat Frequency

Beat Frequency is a really fun module. I don’t really understand how it works!

The knobs, LEDs, and lower four jacks are in related positions. With two signals the outputs and corresponding LEDS can circle around forward or backward at wildly varying frequencies. It’s fun to watch the LEDs. (You’ll see in the videos on the next post.) The output is a mix by the knobs of the positive pulses, making a variable stepped wave at the green Out jack. The 1*2 jack is supposed to be a XOR of the two inputs, but I’m seeing a very small signal there. Maybe needs troubleshooting?

Divine CMOS

Divine CMOS is a type of clock divider.

Divine CMOS reminds me a little of the 5U MOTM 120. Especially the MOTM 120R with the suboctave outputs, but with a bipolar mixer. All panel features are available here, too.