[sdiy] ETI vocoder input amps

[jhaible at t-online.de]

> >> Has anyone been able to complete this vocoder and can 
> help out with the 
> >> two input amps? Alternatively, totally new input amp 
> circuits would 
> >> have to be done to get the project completed.
> >
> >Just to complete irony, I have exactly the same problem 
> with mine! 
> 
> You haven't found the solution yet either? A real bummer 
> this circuit. 

In the schematics, the opamps are drawn wrong.
Both, the second Mic amp stage (= first Line amp stage), and the
EQ circuit (IC 2a) have the + and - inputs mixed up.

The gain switching via TRS jack w/ 2 break contacts is 
a little adventurous, too, but it should work.

So, make the opamp stages linear amps rather than hysteretic
switches - flip the opamp inputs - and your problem should
be solved.

JH

JH.