[sdiy] bitcrusher & friends

[ryan williams]

hi john,

I was making a module that was similar in some ways,  atleast it had 
voltage controlled number of bits. I originally planned to allow audio 
input for this but have not tried that yet. instead it builds a digital 
noise with VC of bits used. the output is scaled based on how many bits 
used so that 2 bits had the same max output voltage as 16 bits, there 
was a lookup table in the AVR for this. it works fine for mine because 
it is 8bit but for 16bit the table wouldn't fit in the atmega8 rom.  the 
VC-bits was just an ADC input to the atmega8. since it is digital noise 
there is also a clock input that would basically be the sample rate.  I 
had a few problems with the way I designed it though (i'm not sure if 
it's a hardware or software problem), It needs more work and I have put 
it on hold for a while.

about tracking filters, this is not too difficult. I used LTC1063 5th 
order switched capacitor filters to achieve this on a PT2395 delay.

-ryan

john mahoney wrote:

>I've wanted to build or buy a voltage-controlled bitcrusher for a while. I
>want it to have at least 16-bits @ 44k, though. Variable sampling rate would
>be extra nice, with anti-aliasing and output filters that can track the
>sample rate and also be VCed. Anybody up for it?
>
>Ingredients: 1 ADC, 1 DAC, 1 Atmel/whatever to read the CVs and shuffle bits
>from ADC to DAC (stripping the low bits as needed). Variable sampling rate?
>Let's see... 1 high frequency VCO, and 2 special VCFs.
>
>I'm thinking that variable sampling rate would cost a lot more. Too much
>more, maybe.
>
>Haven't you mentioned a future MOTM unit, Paul S.? Features...?
>--
>john
>