audio>trigger

[Paul Perry]

At 08:26 PM 5/07/99 GMT, Guido Goebertus  wrote:

>I recently made some 3080 OTA LP filters, and I want to trigger them from
the audio signal supplied at the input.
>I tried some circuits using opams as comparators, full wave rectifiers etc.
but there all slow and have difficult treshold adjustment.
>Can anybody point me to a schemo that offers better performance?
>
this is confusing, do you mean you want to trigger an envelope generator
which then controlls the 3080 filter?

If you are trying to make an envelope follower wah, in which the envelope of
the input signal drives the 3080 
filter, then an ordinary full wave rectifier as in Jung's 'Op Amp Handbook'
will suffice. The ouutput from the
rectifier has to go to a 'voltage to current convertor' to drive the control
input of the OTA filter, if this isn't
part of the circuit already.

paul perry melbourne a*stralia