AW: Re: AW: Re: AW: Re: PCB for MAT-04 VCA

[Haible Juergen]

>      I was able to make a "real" exponential VCA by re-creating the
>      3080-type tri-square VCO exponential converter, and just using the
>      3080 part as a VCA rather than as an integrator. This worked great,
>      although when the gain was unity at CV = 5V, adding to this CV just a
>      little causes the VCA gain to increase very rapidly (exponentially,
>      even!) into distortion. Maybe a zener to limit the CV?

... or simply using a current-limiting resistor from your transistor to
the
Iabc input of the OTA. (Zeners are noisy, and don't really cut sharp at
low
currents)
More in my private mail, but feel free to forward it to DIY if you like.

JH.