AW: harmonics splitter

[Magnus Danielson]

> 
> 
> > is it possible to split a signal into its harmonics (16 ? or 8 ?)
> > in an analogue fashion (no DSPs here)
> 
> Nothing is impossible (;->).
> 
> What about a "tracking filter bank"?
> Detect the fundamental  (the usual fundamental
> detection problems here: zero crossings are
> dominated by formants, not the fundamental ...).
> Use a set of switched capacitor bp-filters,
> and set the center frequencies of these to the
> harmonics with a PLL/Divider system.

One can also build a set of resonators that are either CV controlable or clock
controlable. Having them close to selfresonance will make them reject other
frequencies very well and amplify the tuned frequency quite much, putting 
things
in good balance is necessary thougth, cause if it is too close to selfresonance
it will resonante quite much due to noise (this is a great patch BTW).
If you put a resonator at half and third the tracked frequency you migth step
down to the basic frequency to track that instead of one of it's overtones...

Yet a different approach of detection is to use mixers running at the overtone
spectra and base frequency to detect the amplitude (and some more tricks the
phase) out of each component. This migth actually be an attractive approach if
precision is wanted cause large tunable BP filters easilly blow up in many
components on you (remember, you want a fairly large number of these anyway).
This method is easy to prove the math for as well. It requires a integrator/
lowpass filter at the output to average out the result and suppress the f0+f1
frequency. It's the analogue equalent of an DFT (the general case from which
FFT is derived... fun to derive too :). One mixer per frequency/overtone will
give you the amplitude (althougth phase sensitive) and two mixers will give the
amplitude and phase in forms of the respective rectangluar coordinates...

When will someone do a vocoder THIS way? :)

>  (no, I have *not* built this one (;->) ) 

Juergen... have you gotten lazy or what :)

But then, I haven't build any of mine proposals either..... YET! :) :)

Cheers,
Magnus