[sdiy] spare DG442 cell in modular synth

[Dave Kendall]

Hi all.

I've got a few EFM RXCV boards waiting to be built. Details here ; 
http://www.modular.fonik.de/files/EFMforum/orgEFMfiles/rxcv.pdf
I've already breadboarded a simple offset/scaler to turn the delay 
generator into a simple decay envelope, and have wondered about the 
spare unused section of the (expensive in the UK) DG442 quad switch.

The 3 sections that are used already, are employed to isolate the PIC's 
output from the outside world. It seems like it could be a good idea to 
use the remaining cell of the DG442 as a gate-operated audio signal 
switch. The circuit will be powered from ±15V, so input voltages from a 
typical ±5V modular should be well within range. Apart from adding a 
comparator on the GATE input (which I reckon is a useful addition) is 
there any other circuitry that any of you guys would recommend?

I had thought that a dual opamp wired as a pair of inverting summers, 
one on the input and one on the output would  be a good idea, but are 
they strictly necessary in a ±5V modular environment?

Might there be any crosstalk problems within the chip?

any thoughts welcome,

cheers,
Dave