PWM build

[jmusser]

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html?200528  I've had this circuit bagged up and rattling around for a long time. I finally decide to build it. It has two options for adjusting the pulse width, one is manual, and one is with an LFO that's supplied with the drawing. I made these two options switchable, so I could listen to the differences. My build doesn't sound much like Tim's sound sample, but I do like the tone of it a lot. The "EZ LFO" option I don't care for. I didn't get the chewy sounding effect that Tim got on his sound sample.Mostly, I just got mess. Now, since he does make reference to using an envelope follower or external CV, that may have been just what he used in the sample. The LFO option had a lot less output when you switched over to it, and you had to adjust everything up to compensate for it. When you're in manual pulse width control, you can adjust the tone from pretty boomy and bassy, to mosquito fuzz. There is a huge variety of tones available in the 500K "width" pot. This option is also plenty loud. The tone in my build is more like triggered square wave, and there is not a lot of sustain. The tone is more synthy sounding than Tim's Simple Square Wave Shaper, and if you get used to timing the next note before the one before abruptly decays, then it is a lot of fun, and sounds more like key board than square wave fuzz. Like I said, although, my build doesn't sound a lot like Tim's sample, I still really like the tone of the effect, especially for playing ballad type single string pieces.

[Dan N]

Sounds like mine. I did not use a switch to turn off the lfo. Speed turned down to zero and you get the big volume and tone control with the width knob. Speed up and mucho volume loss and the width knob goes limp.

As a guitar effect I was a tad disappointed by the quick gate. Send a keyboard through it and- magic. Very cool. Also, it can turn an ordinary drum machine into a spitting glitchy nightmare!

[choklitlove]

if anyone is interested, i made a layout for it: http://www.geocities.com/worthekik/pulsewave.html

i breadboarded it the other night.  very interesting, but cool.  i liked it.  i will have to experiment with it a little.  i wasn't able to try pots yet, but we'll see.  i haven't tried the lfo either.

[smnm]

I've been looking into 'taming' mine a bit, just to cut the volume down - I'm thinking of wiring a trimpot as a variable resistor on the power wire, to cut down the voltage. I'm using and LM386 - ll let you know how it turns out.

[Mark Hammer]

One thing worth trying is to marry the PWM circuit and the simple square-wave shaper, also from Tim, by way of Bobby Beausoleil.
Altering the rise or fall time of the waveform, in addition to the duty-cycle would be sonically interesting.  Whether it would be giggable, of course is another thing entirely.  Keep in mind that changes in duty-cycle and alter apparent loudness as "on-time" changes.  Similarly, adding some slope to the sides of the resulting square-wave can also monkey around with the apparent volume.  Between the two, you'll get some neat sounds, but the amount of volume tweaking needed is likely to be a real inconvenience in a stage context.