To understand the functioning of bitcrushers we must first understand the functioning of digital electronics.
Computers use
bits to form the
words that describe
digital information. This is much like the alphanumeric symbols used to form the words that describe Western languages in writing.
Computers use bits because they are easily implemented mechanically using electronic components. (The physical 'on/off' state of a electronic componant gives us one binary digit (bit). Electronic components, like the
flip flop,
gate or
switch, have two states, either 'on' or 'off'. When the components state is on, electricity can flow through, when the gate is off, electricity cannot flow through).
Each sample of a digital signal is described using words formed of bits. Using more bits allows for longer word lengths. Greater word lengths allow a greater accuracy in the description of the signal.
Bit crushers reduce the amount of bits used to describe a signal. A side effect of this reduction is a change to the signal shape, which we hear as ringing.
The ringing is caused by the reduction of the word length (amount of bits) used to describe each sample of the digital signal. As we reduce the number of bits used to describe the sound, the signal becomes 'stepped' (more square like), and the harmonic structure of the signal changes.
So, it would be more accurate to call a bit 'crusher' a bit 'reducer'!
In practical terms, the only method of reducing this ringing is to use filters. If you know the fundamental frequency of your signal, you could use a notch filter to reduce the volume of the higher frequency even harmonics with accuracy. This will reduce the ringing somewhat, but filtering the inhamrmonic signals will still be a problem. If you don't like the ringing, use a different distortion method.
For further information on digital signals, I'd recommend reading the articles found here --->
http://www.bores.com/courses/intro/basics/index.htm and using Wikipedia to follow up on any other terms or concepts that you wish to understand.
(Perhaps Macc or Sharmaji can correct any mistakes in my explanation?)