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. :)

My new environment

Here is my desk in my new room, my new lab PSU, and a new breadboard! :) The oscilloscope is an awful one (old russian model with cyrillic labeling, yuck!), but for a few weeks/months it will serve me, until I'll find a better one.

I've breadboarded the ASM1 noise source, without the pink/random output, because I don't need them for my new secret project. ;) More details later...

Modular Improvization 20100702

A little improvization which is recorded with Audacity into 3 tracks.

Modular improv 20100702 by vinnui

Modular synth improv

YuSynth modular -> MAM RS3 resonator -> Behringer DSP

Modular improvisation 20100407 by vinnui

Power distribution

Simple power distribution boards

The current state of the modular, and the patch from the previous post

Some modular sound

I've played with the completed modules today. Two new half-built mixer modules are in action in this patch, with 3 VCOs, 2 LFOs, and an EMS VCF clone. No additional effects, just some knobbing, VCO FM, LFO FM, etc...

Self playing patch, until 0:45.

YuSynth modular noodle by vinnui

Yusynth VCOs

No tempcos, and no 1V/oct calibration yet.

Started in 2009, but finished in 2010... :)

Yes, my wiring is a mess. :)

My first modular sound sample

I've made a patch on the modular, with 2 VCOs into the EMS VCF, and with 2 LFOs modulating the first VCOs pitch. The EMS VCF's output went out to the Behringer DSP, and then into the computer for recording.

Some manual knob twiddling...

Lossless sample here.

YuSynth EMS VCF ready!

My first VCF is ready! The YuSynth EMS VCS3 diode ladder VCF clone is a cool sounding filter, and it has special resonance behavior. Based on the YuSynth section of the E-M forum, the value of the resistor R41 may need to reduced, to match the 2N3819 JFET characteristics. I can't able to reach self-oscillation with the standard 680K, so I reduced it to 220K and then

to 180K, which is finally correct.

The TL074 which I've used was faulty, so the control and the input levels are started to wiggle after a few minutes, and large amounts of noise went to the output. After some "air cooling", the levels are normalized, and the noise was dissapeared, at this point I've realized, that this opamp need to be replaced.