Exp Converter

[Jelle Plantenberg]

Hello,

I'm trying to build the 6/12/18 db/oct LPF as found on the Synth diy page
(http://www.uta.fi/~helin/) and, since it didn't work the first time (of
coarse), I'm currently in some sort of testing fase. I reduced the scematic
to the first part (only 6 db/oct) and am expiriencing difficulties with the
exponetial converter.

The scematic says "replace with exp CV converter", which I found on the
same page. When all of it didn't work I simulated the converter in
Electronics Work Bench and it gave a constant output when I feeded a 1Hz
triangle between 0 and 10 volts, which can hardly be the goal...
I then tried the CV converter as found in the original scematic, but still
no results. When directly feeding a CV into the 22k resistor connected to
pin 5 (bias) of the CA3080, I find the audio results not very satisfying
(no filter change, more of a gain change)...

I hope that someone is able to help me, or that someone has build the same
VCLPF and is willing to share some info (about the exp converter for
example) about it.

Regards,

Jelle
____________________________________
 J.H.Plantenberg at student.utwente.nl