Patch of The Week: Audio-rate PWM - Big sounds from 1 VCO using extreme Pulse Width Modulation

video upload by AJH Synth Official

"Here is how you can make a single oscillator sound huge using pulse width modulation at audio rate - using a normal-speed VCO as a mod source rather than a dedicated LFO. Frequency Modulation (FM) synthesis uses the same principle, but modulating the pitch of a waveform at extreme speeds to create additional harmonics, and thus an entirely new sound. Here we are modulating the shape of the wave itself, which also creates additional harmonic content and produces a new and more complex timbre. This process requires a fair amount of experimenting and fine-tuning, but the results can sound massive.

Patch Sheet PDF: https://kvisit.com/8AE/zvYG
(Patch Notes duplicated further down the page)"

Index:
00:00 Intro
00:12 Sound example
01:00 Setting up the Patch & How it works
03:24 With a Sequencer
04:27 Patch Sheet

PATCH NOTES (Duplicated from the PDF file)
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Green dots show approximate pot and switch positions. Pots and switches that do not have green dots are not used in this patch, and should be left at their zero or off positions.
In the video I'm using the Glide + Noise MkII module to access the CV bus, allowing me to control VCOs 2 and 3 from one input/cable, otherwise you will need to use a multiple or stacking cables to connect the keyboard/sequencer to VCOs 2 and 3, as is usual with a fully modular synth.
An unconnected cable (nothing at the other end) is connected to the 1V/Oct input of VCO 1 in order to disable the CV BUS from changing it's pitch. If you are not using the CV BUS to control VCOs 2 and 3 then you do not need to connect this cable.
VCO 2 will need careful fine-tuning to get it's frequency at a point where it compliments VCO 3, which it is modulating. The desired point will be when the sound from VCO 3 becomes comparatively smooth, rather than a course, beating timbre.
The CV MIX module is key here for combining the 2 modulation VCOs. You could use any 2 channels, but bear in mind that 3 has a higher gain level, 1 becomes a bi-polar voltage source that can be added to the output if nothing is connected to that channel, and 4 can be used as an offset to the output when it's switch is down.
VCA: In the video I use a Muting Mixer as final output VCA, so in the diagram I show the Discrete Cascaded VCA being used for the benefit of those who have one, but in either case set master to full then gradually increase the input level.
Modules used from top-left to bottom-right: Glide + Noise (for bus board access - optional), VCO 1 & 2, CV MIX, VCO 3, Transistor Ladder Filter, Contour Generators, Discrete Cascaded VCA (or Muting Mixer).