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
- a simple version
- a voltage-controlled version
This product was added to our catalog on Monday 26 January, 2009.