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Prismatic Ray Saw Waveform
MUFF WIGGLER Forum Index -> Video Synthesis  
Author Prismatic Ray Saw Waveform
You may have noticed that the Prismatic Ray doesn't have a sawtooth wave output. Well, there's a really simple waveshaping technique that'll add one. It only takes half a Bridge.

Take the triangle output from the PR and feed it into the mixer on the Bridge, set to invert. Feed the output and the original triangle into the Crossfader, using the square wave to switch between tri and inverted tri. Adjust the pedestal and gain controls on the PR until you have a sawtooth. (Pedestal at 12 o'clock worked for me.)

You can use a multiple to split the tri to avoid any voltage drop. I'm happy with the results from a passive split, but you might not be. Also, you might want to use the tri at the same time.

As a bonus, you can warp the sawtooth wave just like the triangle wave. razz
awesome tip, using the bridge like that has a lot of good applications.
Compact! I tried this with Cadets and got pretty close results. It seemed like the phase was slightly off between the square and triangle waveforms; couldn't quite duplicate the first half of the triangle. Did you notice any issues like that with your method?
Before I tried it, I wondered if I'd have that problem, but I was pleasantly suprised to discover that the square phase was exactly right. I don't know if this was by design or accident, but I'm really glad the PR works this way.

The inspiration came from selling my last VWG modules and wondering if I could get a saw by external waveshaping. I looked up some schematics for triangle core VCOs and found (saw lol) how they worked. So I worked how I could do that with LZX modules and tested it. This is the technique that worked.

As I said earlier, you need to fiddle with the pedestal and gain controls to get the saw. You may see a small glitch halfway, but apparently that's normal for a tri core VCO. You can't really expect perfection where a switch is being used. There'll always be some noise.
I'll have to wiggle some more!

I found this thread to try to achieve the same results. Dave Jones posted a reply with loads of nice info, and a really great diagram as well! I have yet to try mixing the square back with the saw created by inversion.
Try this!! Just feed the square out into the Multiply VC input. Make sure to enable 4Q mode, this allows inversion of the triangle wave via the Mult VC in.

I also kept pedestal at 12 o' clock. Multiply VC and the "master" multiply knob were always opposite, alternating this relationship got the opposite ramp/saw direction. For example, with the Mult VC fully CCW and Multiply knob fully CW, my saw starts at 1V and decreases to 0V.

Hopefully these pictures illustrate my words!

Yes! That was one of the threads I read while researching this topic. Lots of useful info, esp the tri to saw link.

Also: top demo. Thanks. applause I should post some screencaps of my own saw wiggling.
So, I couldn't just post a simple demo...

Yes, I know they're different sizes. Mr. Green
Looks great! applause
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