Is there any synth that can do roland's Saw PWM?

[cytospur]

Is this close enough?:

Saw PWM.png

Top is DUNE3, middle is Redominator, bottom is an overlay of the two (DUNE3 in cyan, Redominator in magenta).

[gentleclockdivider]

lol , that's the other alpha juno waveform which doesn't do pulse width

[cytospur]

lol , that's the other alpha juno waveform ( sort of )

Which one are we talking about?

[gentleclockdivider]

Instinctively I would have imagined a saw waveform more like this

Yeah instincts

[e-crooner]

Instinctively I would have imagined a saw waveform more like this

Yeah instincts

Instincts trained by real pulse signals

[cytospur]

This?

Saw PWM2.png

Subtle differences are due to filter settings I think.

[gentleclockdivider]

You can’t really do the juno formant osc in dune 3 because the unipolar saw has to be the sync master .
It also amplitude modulates the square waveform , iow the saw is not audible it does a windowing function on the square .
Or you could use a clipper to get rid of the negative portion of the saw .
Will try tomorow and build it in reaktor .

[cytospur]

You can’t really do the juno formant osc in dune 3 because the unipolar saw has to be the sync master .
It also amplitude modulates the square waveform , iow the saw is not audible it does a windowing function on the square .
Or you could use a clipper to get rid of the negative portion of the saw .
Will try tomorow and build it in reaktor .

That's exactly what I've done in DUNE3. I've used a unipolar saw, which is curved upwards (using the wavetable equation editor), to amplitude modulate the square waveform. It also has the unipolar saw added to the amplitude modulated square.

This was the formula that I used for the unipolar saw: (0.5*x+0.5)^0.75 (for x from -1 to +1).

[aciddose]

You won't be able to produce the same outputs because amplitude modulation will create aliases. This would require a similar ultra-high sampling rate as the juno synthesizers use (~1.536 MHz). As a point of reference, this would be 48k * 32x oversampled.

Note that the juno synthesizers produce an entirely digital pulse wave which is the frequency source for the oscillator waveforms. There are no "alias" harmonics because the harmonics of a pulse waveform are perfect. So long as the "clock" frequency (whatever MHz) is divided by whole integers (2, 3, 4, ...) and high enough frequency to start with, this provides reasonable frequency precision without aliased harmonics despite being fully digital/discrete.

[aciddose]

Please see here: viewtopic.php?p=5875016#p5875016

The easiest way to synthesize these waveforms in software is almost definitely the "windowed-sinc impulse convolution"/"minBLEP" technique or a related technique.

In these we take primitive shapes (edge = zero order, line = 1st order, parabolic curve = 2nd order, ...) and "draw" the segments directly. On each "point" between segments we insert FIR filter kernels/impulses and negate the naive step to anti-alias the result. This produces close to ideal output, although it is moderately complex to implement.

[Unaspected]

So not like this:



Which is what I would think of for PWM of a sawtooth - and also how PWM could be applied to any waveform when reading from a wavetable.

But more like this:


(central line is zero)

Which is this:



When the square wave is running at a multiple of the sawtooth.

I'm presuming that the output saw is bipolar. And I missed out the square sub but can see how that would work to further change the tone and output shape. Are independent controls given for the sub PWM or is that synced to the same PWM parameter?

As you can see, these will happily alias as the square was created from a simple logic test and neither waveforms are filtered - so the vertical edge is hard (and invisible) - effectively, the value jumps from one value to the next with no interpolation.


For pure visual entertainment - and because it might help some to understand how bipolar waveforms can invert a portion of an enveloped waveform if they are not scaled and shifted into a unipolar form...

Here is a unipolar saw enveloping a bipolar square:



And a bipolar saw enveloping a bipolar square:

[gentleclockdivider]

First animation is used in phase distortion , distorting ramp- phasor reading cosine from look up.