Diva synth – tutorial on pulse modulation
The fourth in our series of bite-sized tutorials aimed at users of u-he’s Diva, this one is all about the ever-popular “pulse width modulation” (PWM) effect. PWM was traditionally used to add tonal movement — especially useful for synths that only had one oscillator e.g. ARP Axxe.
Act I – standard PWM: How to set up typical cyclic PWM in the various oscillator models. The ratio between the upper and lower levels (“mark space ratio”) of a rectangular waveform is slowly modulated by an LFO. Note: One of the sawtooth waveforms in the “DCO” oscillator model also delivers a similar effect, but I neglected to demonstrated it in this video!
Act II – the very first PWM is likely to have been an attempt to emulate the satisfying “zippy” sound of two detuned sawtooth waves, one of which is inverted. Because the Triple VCO model features a Ramp wave (i.e. inverted sawtooth), it’s worth trying this out in Diva. A taste of history, this method is my personal favourite.
Even if your 2-oscillator hardware synth didn’t have a ramp wave, you could still make similar sounds by detuning two pulse waves – as shown here.
Act III – “sync” i.e. oscillator synchronization means that the phase of a slave oscillator is reset by a master oscillator. If you modulate the pitch of the slave within a very narrow range, you can get effects that are very similar to PWM. This method requires some practise…
Homework: how dense can can make your PWM sound by stacking and detuning 2 voices (no more), and using the Voice modulator to offset pulse widths and even the LFO rate? Read that again…