[sdiy] Anyone built the ELEKTOR VOCODER?

[jh.]

> I actually found the trick in another Elektor article (spectrum analyzer),
> and it consist in detuning slightly the central freq of each filter, so
that
> Fc of filter 1 is the central freq of the band, and the central freq of
the
> 2 other filters respectively the 2 cut freqs (high & low) of the band.

Don't underestimate the problem.

A spectrum analyzer "only" needs the 3 partial filters of each channel
to be fitted together in terms of phase and amplitude
(resulting in different center frequencies and Q factors).
This is "easy", because you don't sum up adjacent filter bands !
In a vocoder, *all* partial filters interact, so you don't have to fit
groups of 3, but groups of 9 at least (if you go for a 6-pole design).

The slight difference between analyzing (and dropping phase
information) and doing synthesis.

JH.