DSP Robotics Support

The answer to that is yes, to everyone - as stated in my original post.

Hi all -

Gotta question, especially for Spogg and/or Martin Vicanek: Do either of you recognize the code for this Saw osc; I think I 'lifted' it from a schematic during my brief Flowstone trial period and I ID'd it at the time as a Vicanek oscillator, but there is no text string inside it identifying it as such, as there is in his low-CPU/low distortion Sine osc. I've found that the sine osc sounds much better than the stock sine osc when used in a Carrier/Modulator FM (phase modulation) pair. Also the Saw exhibits no ringing or overshoot when seen on a scope -very clean. I'd like to include in the schematics credit to Martin if he wrote the Saw as well; if not, whoever did. I'd also like to give credit on my website.





Also, does anyone know of a similar code saw that can be used for PWM - this one can only be phase-shifted at exactly 50% (to make a square with another saw); at other angles it flies into wild distortion. And has a Sync input?

Thanks

This is Martin's work for sure, so he'll need to answer your questions Kevin.

Cheers

Spogg

Yup, that looks like mine indeed. Funny typo there, haha: <90% harmonic distortion should read < 90 dB.

Not sure what you mean by PWM for a saw? For me the P stands for "pulse", so a square wawe. What would be the pulse width of a saw? Although you can do morphing which sounds a bit like PWM.

About the sync input: I deliberately didn't include a sync input because it causes quite severe aliasing (try it with the stock osc!). To emulate the sync sound of an analog synth in the digital domain is a bit tricky, because the sync point generally falls between two samples. It can be done, but not in a neatly encapsulated general purpose modular fashion.

Hi Martin, thanks.

What I meant was when using this saw osc to do PWM by the usual way of mixing two saws, inverting one and shifting it's phase to create various pulse widths, the oscillator goes wildly into distortion when the phase shift is anything but exactly 0.5; so can't produce pulse waves with it - only square.

I'll go through the synths I've used them in and add a credit to you in the notes. Great work - the sine makes very sweet-sounding phase modulation.

I know sync with the stock oscillators is pretty hashy, but it's a useful alternate tone color anyway.

Thats odd! Pwm should work that way with any saw. Will check later.
Edit: No problem here with PWM. Please post schematic which demonstrates the problem that you are getting.

Is there another way of doing PWM? - these are the only two I know of. How are you doing it?

Sorry your images came out pixelized. Anyway, here is a little demo, hope it helps.

Thanks for that, but I can't open the schematic I only have SM. I tried combining the saws with a stream subtract but get the same thing you see in the images I posted. Is your Phase control just a 0-1 de-zipped knob? And the Multiply module - just an attenuator? Is there anything in those Saw modules other than the code itself?

In general, is there an advantage to doing PWM with a steam subtract rather than mixing the phase-shifted saw through an inverter?

About the images I posted - there must something I'm not understanding. When I try to post larger, higher-res images I get a warning that they must 600 pixels on the largest dimension.

Good Lord!

I appear to have spogged one of Martin's schematics! We live in strange times for sure



This small modification means the PWM waveform's offset won't change with the pulse width control value. The output is more like an analogue circuit, which passes a ramp through a level comparator.

This modification should reduce modulation breakthrough effects.

Cheers

Spogg