[sdiy] Really Low, LFO

[cheater cheater]

Hi Paul,

On Sat, Apr 3, 2010 at 02:57, Paul Perry <pfperry at melbpc.org.au> wrote:
> when one speaks of 'filtering' the output...
> filtering takes on an intersting turn when the freq is .001 Hz or so!

What do you mean?

Kyle,

On Sat, Apr 3, 2010 at 01:19, Kyle Stephens <lightburnx at yahoo.com> wrote:
> Jay - good point on the precision op amps, figured that would come into play.
>
> Cheater, I got the term from my dad, an EE, has often thrown around "second order interference" in regards to stuff I've built

Hmm, cool :-) I bet your dad is very helpful to your hobby here! Think
you could ask your dad if this term is defined with any books he can
come up with offhand?

Tom,

> I agree with what others have said, it isn't hard to do *low* frequencies with digital.

Well... depends on the waveshape. A sinewave is not trivial to get
going: either you need to have a *huge* table of values (not going to
happen) or need a good interpolator, or need an algorithmic way of
deriving the sinewave. But given the very low sampling rate that you
can get away with (you only need 2x freq of LFO... so not a lot!), you
can make those algorithms as good as you want. The problem is that
it's fairly boring math that, chances are, you won't use anywhere else
in life - this is coming from a mathematician who normally finds
boring stuff fascinating - so, if someone just wants an lfo with basic
shape, I strongly suggest not reinventing the wheel and having a
*good* look at specialized function generators

D.