My first multitracked "music" with the DIY modular

In this song i've used the following YuSynth modules: VCOs, EMS VCF, ADSRs, a mixer, and a VCA.

Magic Smoke 8K LFO

For the next module, which I want to build, i've needed a simpe LFO with speed control only. After hours of browsing the schematics, i've found Tim Servo's MSE 8K LFO. This circuit can do triangle and square waveforms, and it's high range, but with only one pot it's hard to fine tune on the lower end. The schematics shows a fine tune pot, but i don't want to include it, because of the limited front panel space.
It's very easy to build, only a TL072 or 074 opamp is needed. I've integrated a simple led driver too.
With polyester caps, the triangle waveforms are perfect, of course ceramics don't do it very well.
My version uses 1nF timing caps, and this gives 15 sec with the lowest pot setting, which is perfect for me.

More schematics, simple LFO's, and waveshapers for this LFO are here.

Thanks to Tim Servo, for his great work!

Schematics

Dual LFO's on breadboard

Only a 1M Log pot, and an LED

Some power distributors added

My new module: Mixer, MidiCV

This is a combined module, which contains a 6 input mixer, a monophonic Midi2CV converter (MCV-628), and an input preamp.

My new, non-standard panel format is 160x160 mm, fixed. I've bought a 20 aluminium panels, and I will repanel the old blue modules. I need to do this, because the old panels are weak, and inaccurate.

Drum synthesizer - construction 3

The front panel is ready, and the drum synth has a new PSU too. The electronics is completed, now I need to design a case.

Drum synthesizer - contruction 2

I've finished the rewiring of the panels, and the drum synth is now working with it's own external 9V DC PSU. Two separate piezo triggers can be used to fire the channels independently, it's a lot of fun. :) Sadly, the DS8's output signals are too quiet, or not ideal for the Wasp VCF, even if resistor R30 (100K) is replaced by a 470K one.

I also need to process external signals, so a preamp will be included:

Preamp, and mixer circuit on veroboard:

Drum synthesizer - construction 1

I'm in the middle of the building phase. The two drum voices (with the Wasp filters) are working properly! :)

I've made a temporary, cardboard faceplate, because I need to finalize the graphics. I need to make an extra PCB with the VCF LFOs (4069 LFO), some preamp for external input signals, a 555 negative supply circuit, and maybe a headphone preamp too. I also need to make some experiments with cross-VCO modulation between the two DS8s. If it sounds good, I will put 2 pots on the front panel with this functionality. I will make experiments with Wasp out -> DS8 VCA in feedback loop. I like distortion... :)

The "Rebel.D2" drum synthesizer

I like to run projects in parallel, so there is my new idea: I want a simple, analog drum synthesizer.

I've built a Coron DS8 clone from Marc Bareille's schematics. I don't have CA3080 OTAs, so I've redrawn the circuit to use LM13700, and integrated a led driver for the incoming trigger signals.

After a few hours of playing with the DS8, I've realized, that this circuit can be enhanced with a VCF. The DS8 doesn't contains a filter, only the noise spectrum can be altered with a switch.

Because the DS8 is using +5V supply voltage, and the Wasp VCF also using this value, I've tried it, and built this combination, plus a piezo trigger pad into a temporary plastic case for trial.

This combination sounds wonderful, warm, and analog, but it also can be harsh, distorted and rude. This VCF simply mutiplies the possibilities of the DS8.

Then the idea of a simple two channel drum synthesizer was born:

I don't want to integrate any control circuit into this machine, only the CV/control/trigger jack sockets will be built in. The Wasp filters can be used for external signal processing, so this unit will be an integrated drum synth and a dual filterbox.

Constructing the modbus

The VCAs of the modbusses are simple YuSynth VCAs. I've redrawn it in Eagle, removed the led driver circuit, and added simple LF412 CV buffers:

More wiring and testing needed.

The concept of the modulation bus

The idea of the modulation bus is came from the Minimoog Voyager, which uses this simple idea, to enable the user, to quickly dial in modulation settings. The Voyager came with 2 independent modbusses, with slightly different capabilities, and the Voyager Oldschool (which is 100% analog, without the digital patch storage, and control) uses modbusses with even more control possibilities.

The Minimoog Voyager's modbus:

The Minimoog Voyager Oldschool offers more sources, desinations, and controller/shaping options, which makes this instrument more flexible:

The user can select a modulation source with the "source" selector, the modulation destination, and then the controller, which will influence the modulation, like the keyboard velocity, or an external pedal. Finally, the amount knob makes possible to set the intensity of the modulation.

I think, this idea is very useful, even in semi-modular synths. No patch cables are needed, many of the modulations are possible with a few simple settings, and they are easy to remember.
I've started to experiment with modbusses in my monosynth prototype. In my current setup, the modbus needs to be more flexible than the Voyager's modbus, because my synth has more CV sources, and more possible modulation destinations. My implementation of the thing looks like this:

Every modbus needs a VCA which passes CV signals and audio signals too (has no blocking capacitors on the inputs), and rotary switches to select source, destination, and shaper settings. I'm using 12 position rotary switches for the dest/source/shaper settings. The amount knob controls the VCA's input CV level. If the amount knob is set to the maximum, the VCA's output level is maxed, and if the knob is set to zero, the VCA's output is totally silent (no modulation).

The useful setup for me is the following for modbus1:

• Sources: VCO1, VCO2, SUB osc1, ENV1, ENV2, LFO1, LFO2, LFO3, Mixer output, Saw anim CV1, Saw anim CV2 (they are simple LFOs), and Keyboard CV
• Destinations: VCO1 frequency, VCO2 frequency, VCO1+2 frequency, Mixer input, VCF cutoff, VCA1 CV, VCA2 CV, VCA1+2 CV, ENV1 trigger, ENV2 trigger, SawAnim 1 CV, SawAnim 2 CV
• Shapers: Keyboard CV, Keyboard AUX (f.e. modwheel), ENV1, ENV2, ENV1 inv, ENV2 inv, LFO1, LFO2, LFO3, SUB1, SawA1, None

Modbus in steroids :)

My modulation busses allows the extraction of the final modulation signals, and the injection of an external source or shaper signal, which makes them integrate with the patch panel of the synth.

Frontpanel prototyping

Ugly little cardboard box. :)