[sdiy] Really Low, LFO

[Antti Huovilainen]

On Fri, 2 Apr 2010, dancemachine at gmail.com wrote:

> really? that's where I would be more worried about it. think about it. 
> the finite changes in output could be stretched to the point where you 
> have enough time to hear each one. analog has no steps.

Neither has digital if you do it properly (which is not hard at all).

Use a somewhat higher samplerate (say, 1 kHz), add a simple RC lowpass 
filter at 1/20th that frequency, and use software dither for the DAC 
output. Add first order error feedback (trivial even with 8 bit mcu) and 
you remove almost all of the noise below the RC filter cutoff.

Not that anyone would hear the "click" of a 12 bit DAC step even without 
dither as long as you used the RC filter.

Antti

"No boom today. Boom tomorrow. There's always a boom tomorrow"
   -- Lt. Cmdr. Ivanova