BugCrushing

Here are some early BugCrushing designs (from mid 2006) I came up with based on the Analog Devices AD781 chip. Since then I've moved on to using switch ICs due to the difficulty of getting the AD781 - many ideas carry through though... BugCrushing is basically just the audio effect of sample-rate-reduction. Here's what I wrote before:

I'd wanted to make some sort of bit-crusher effect for ages, but never quite figured the way to use microprocessors or ADC/DACs. And then I came across the Analog Devices AD781 Sample & Hold Amp and it struck me that running this at audio rates would effectively give a simple means of changing the sampling rate - not true bit-crushing but it sounds great!

The AD781 is very easy to implement. All you need is a 5v trigger pulse at whatever rate - this must, however, be of very narrow pulses, so I used a 40106 chip (with 5v supply) to make a narrow pulse osc. You also need to keep the pulses narrow to avoid signal bleed through. From this point I added a Voltage Controlled Resistor onto the circuit to make the Trigger Osc voltage controllable. These circuits were designed for my modular system - they run off a +/- 12v bipolar supply

The 1st circuit is the simple stand-alone - simple & very effective. The 2nd circuit adds voltage control to the 1st circuit (along with some tweaks for the particular application). An LM13700 is used for a floating VC Resistor (resistor values found by trial & error!) and this is driven by a log converter based on a Ray Wilson Music From Outer Space schematic.

I daresay there's some refinements possible....

Steven Roeder has done a very compact stripboard layout for the stand-alone BugCrusher circuit - find it here