When I had posted the question it was 3 a.m. here in Italy so I went to bed. This morning I found at least three valid approachs suggested:
1)mixer 2)RM input 3)LH's mod to the unit.
Thanks to everyone... who knows maybe Paul will comment LH's suggestion. Enrico
--- In motm@y..., "J. Larry Hendry" <jlarryh@i...> wrote:
> ----- Original Message -----
> From: edibennardo <endiendi@t...>
> I was happy enough with my VCA till I wanted to have both an EG and an LFO
> controlling it... Any thoughts? Any suggestions about a possible mod adding
> a second CV maybe with an attenuator too?
> Enrico Italy
>
> Larry Hendry writes:
> OK, I'll take a shot at this. If I understand the circuit correctly, the
> voltage applied at PIN 12 of the 3330 controls the overall gain of the VCA.
> Paul has already built a summing node on the front end that sums the voltage
> from the GAIN pot to the voltage from the CV MOD pot. I see no reason why
> you could not add a 3rd input to that summing node. The only problem is
> that you could end up with a resulting voltage that drives the VCA into
> clipping if you turn both controls to max.
>
> As I see it, the modification requires only 3 parts. 1 - add the input jack
> 2 - add a CV2 mod pot, connect the pot and jack just like J1 and VR1. 3 -
> add a resistor from the wiper of new pot to the common point at R1 and R5.
> Since a LFO is typically 10 volts swing, I think this resistor should be
> 100K or somewhat larger. 100K would cause this CV input to have about 50%
> of the effect as CV input 1 (as I see it).
>
> It seems to me if you use the LFO input, then depending on whether you have
> a "+/-" or "0 to -" voltage you might have to adjust your "gain" pot off of
> the "0" set point some.
>
> Paul, Care to comment right or wrong?
>
> Stooge Larry
>
> Disclaimer: I am not an engineer. I am not telling you to modify your
> MOTM-110. I am offering this modification suggestion for the purpose of
> discussion and learning.