PWM Preferences!

humancalledjohn

Hello all, welcome

I've been working on the rough schematic for a VCO similar to the René Schmitz 4069 VCO in simulation. I have included extensive waveform outputs, with things like the alpha juno PWM sawtooth as well as standard pulse waves, and am wondering about the best practices for pulse width modulation control.

How do you people like the ranges of your PWM CV? clipped to a range of say 5-95% pulse for constant sound? able to cut out completely for rhythmic gates? passed through a wavefolder so the changes reverse direction just before cutting out?

I'm not sure myself as I don't have much modular experience as of yet. I am considering adding a switch to toggle between modes but that feels like it would raise the amount of board space and front panel busyness too much to justify. I suppose the most flexible option is able to cut out completely mode and using external modules to implement the other functions, but my planned modular is quite small and if you have that capability you can probably also just use an external comparator on the sawtooth.

I'm probably overthinking here, but your opinions would be very helpful here. Bless me with your wisdom, o wise synth veterans!

Anyone with general advice about modular diy (decorating front panels, etc.) would also be appreciated. Also I think this is the right place to ask this, but please advise if otherwise. Sorry for the long post!

blue hell · Posted: Fri Oct 09, 2026 8:46 am Post subject:

I'd just make it one way or the other .. it would not be too hard when not quite happy with the choice to change the pwm range at a leter stage .. like .. at most two resistors to be changed? no?

mosc · Posted: Fri Oct 09, 2026 6:34 pm Post subject:

Great questions. I doubt if there is a single answer. My experience with pulse width modulation is two-fold.

Most of the time I like using it in the mode where it doesn't silence the oscillator. When using oscillators in the usual way the gateing is done down the road in the patch chain with filters, VCAs, frequency and ring modulators etc.

That said, it can be thrilling when you can drive the PWM osc to silence through the control voltage inputs, especially at audio rates. It becomes something special. Feedback opens possibilities too.

So, I'd vote for the switch. Add that to the choices and I'll vote for that. Cool