I got this PCB in a trade with Mitchell over at Super Freq (http://www.super-freq.com/pcb-projects/pwm-build/). This is his implementation of Tim Escobedo's "PWM". It includes the optional LFO. It's a square wave synth with modulated pulse width. In a track it could be mistaken for an old analog synth.
(https://live.staticflickr.com/65535/54393108038_5b1f6a7737_c.jpg) (https://flic.kr/p/2qSwTZy)
I tried a spray-can finish for the first time in a long time. Historically, I've had a hard time getting the paint to adhere. I'm optimistic that the few tricks I've learned over the years will help. Aesthetically, I wanted it to look like a Lisa Frank fever dream about fuzz.
(https://live.staticflickr.com/65535/54392879196_833a6a5fd3_c.jpg) (https://flic.kr/p/2qSvHY1)
You could fit all the components in a 1590A. The extra room is for all the attitude.
(https://i0.wp.com/www.super-freq.com/wp-content/uploads/2022/02/PWM-Schematic.png)
Of course, I can't leave well enough alone, so I made some mods.
- I swapped lugs 1 and 3 of the Rate control so that clockwise was faster.
- I jumpered the LFO switch and opted to put a big-ass 10mm bypass LED in its place. Setting Depth to zero still kills the modulation.
- I changed C2 to 6.8nF and added a 47k resistor between lug 3 of the PWM (labeled "Width" on my build) and ground. Without the minimum resistance, it's possible to set the pulse width so narrow that the signal cuts out entirely.
- I changed C2 to 10uF and R2 to 4.7k. This widens the range of the LFO.
All and all this is a fun circuit and unlike anything else I've built!
Nice! That's a really cool circuit.
I've always liked small boards in large enclosures.
How do you like the sound with the LFO going?
btw, when you first posted this, I don't think it showed up in my 'Unread Posts'?? Just thought I'd mention it, I don't know if others have had that happen.
Quote from: NorthCoast on March 27, 2025, 04:05:30 PMHow do you like the sound with the LFO going?
At first I thought a slow setting would sound good over heavy riffing, something akin to EVH with a phaser, but something about the modulation tends to obscure the rhythm. Medium to fast sounds good on single note lead lines. Sounds like a synth part!