[sdiy] LFO question

[ChristianH]

Hi,

just a foggy idea: what about using a micro controlled current
source/integrator, in order to fill the steps. Since the controller
always knows the desired frequency, it could adapt the slope to match
the step size. That would make filtering for a smooth output easier.

However, using only a current source to generate wave forms (without any
feedback into the controller) would most probably suffer from symmetry
problems, causing DC level to run away.

And using 2 DACs for coarse voltage output and a DAC controlled analog
linear interpolation would only be justified if you're going for a more
complex LFO than the ordinary tri/sine/square one. That is, unless you
have multiple cheap DAC ports anyway, e.g. PWM generated analog outputs.

regards
Chris


On Wed, 29 Jan 2003 11:13:53 +0100 Michael Buchstaller wrote:

> 8 bits are definitive not enough for a LFO, IMHO.
> (thinking of low-speed 1Hz modulating filter cutoff or pitch - that
> would be an incredible amount of zippering)
> 
> for higher speeds, or very small amounts of modulation,
> it might be OK.
> 
> 
> -Michael Buchstaller