Hypoxiac - bitcrusher with a switched cap filter

I got some MF4CN-50 switched cap filters to mess around with and found a fun new trick. The chips take ultrasonic square waves to create tight 4th order low pass filters. However, passing them an audio frequency square wave as well* creates aliasing or sample rate reduction (sometimes called "analog bitcrushing").

*You have to send both square waves for the chip to work, it needs that fast filter frequency. Simply pinging both waves at the chip didn't work for me, I had to modulate the fast wave with the slower one.

I'm fairly certain the aliasing happens because a sample and hold circuit is also a switch before a capacitor.

Scroll down for schematic & stripboard...

Schematic

In this design (and the video) I'm controlling both square waves with a dual gang pot. I prefer audio with lower sample rates to be low pass filtered anyway, so this is a tidy solution.

The op amp is there mainly for make up gain after the filtering, though a simple transistor would achieve the same thing. The input buffer is especially useful for a guitar pedal, though in an earlier design I went without the op amp and built on the basic schematic from the filter chip's datasheet. The 1m resistor in that design is looking very pedal-input-buffer-y, but there's no schematic of the chip's insides so I can't say whether it's buffered or not.

The optional unity gain dry signal is just a thought, it wouldn't always be at unity gain considering where the volume pot is. It's omitted from the stripboard layout.

Stripboard

Note - this layout is designed to have the dual gang pot soldered directly to the stripboard, cutting down on fiddly wiring. The body of the pot goes to the left of the holes, on the component side. Check the video if that needs clarification!

This is the layout I use in the video so it's confirmed to work :)