Introduction

The Digitizer is a digital bitcrusher pedal that I designed last year. I originally decided to make a bitcrusher as I was looking to get back into pedal building with a more unusual effect, and I’d become very interested in digital sampling and the tonal qualities of vintage samplers. I figured that a bitcrusher pedal would allow for these effects in real-time, rather than having to record audio into a machine and then play it back again.

None of the other bitcrusher pedals around were quite what I was looking for – I wanted it to be able to get very lo-fi and distorted, but I also wanted it to be able to be very subtle and musical. The stock bitcrusher plugin in Logic Pro was a big source of inspiration to me as a particularly good implementation of this effect.

Controls

Of the relative few others around, several cheat and aren’t a true bitcrusher (I know, we’re reaching peak levels of snobbery here!) and are in fact just ‘sample rate reducers’ – although admittedly this a large part of what makes up the bitcrusher sound. The Digitizer is fully digital and presents your digitized audio in sparkling 4/6/8 bit fidelity at a user-controlled sampling rate. The LEDs on the panel provide a readout of the data going through the processor – they’re mainly there for visual appeal but they do also serve to show that the incoming signal is at the right level.

For greater control over the sound, a simple low pass filter is provided for the wet signal, as well as a mixer to blend between the wet and dry signal. The bypass action is true bypass, driven by a relay, and it can be configured to work in either latching or momentary modes by holding down the button at power-on with the toggle switch in either the up or down positions respectively.

The preamplifier in this ‘Revision 2’ Digitizer is slightly improved since the original, it now has a gain trimmer (inside on the circuit board) so you can tweak this to taste. It’s also much more immune to noisy / hum-inducing power supplies.

How It Works

All of the processing is done with a 8-bit AVR microcontroller. It samples the incoming signal from the preamplifier as fast and as frequently as possible, and then sends it straight back out again to the DAC, at an adjustable interval determined by the position of the RATE knob to drop the sample rate. The sampled data is 8-bit, although this can be reduced down to 6 or 4 with the BITS switch. The LEDs are updated 200x slower than the audio sampling rate. This gives them more of a blinking appearance, as at audio rate they just appear solidly lit.

The microcontroller also manages the bypass switching. As mentioned previously, the bypass switch can work either latching or momentarily. The setting is remembered and recalled at power-on.

Photos