AW: re : vocoder

[Haible Juergen]

>I have made a variation simulation on a Bessel LP
>already, and (as assumed) it shows little deviation.
>That is the big advantage of multi stage filters
>with Bessel low Q settings : They are not very
>*instable* designs in terms of R & C tolerance.
>(It turns out that a higher order,low Q design
<is much more stable than a low order high Q design.
<The pole location get's realy important in a
>2dB ripple Tcheby, because high q sections need
>perfect matching with low q sections to achieve the
>proper characteristic. The high Q peak is very
>sharp, and easy to miss in case of tolerance.
>Also the op-amp open loop gain is not so critical
            > in the higher order case, isn't it ?

Sorry that I haven't read your original posting as carefully as I should have.
You wrote about Bessel filters, and I lamented about the trials of staggering
and ripples in an (obviously) tchebychef design. Sorry.

Keep us informed how your project is going on in the future!

JH.