[sdiy] Design helps from the masters...

[Peter Grenader]

Guys/gals,

As possibly stated before, I am a hack circuit designer.  But a hack in need
of a little assistance, if you can fancy my question for a sec:

I am in need of a comparator circuit which will allow me to basically
selectably enable a gate or trigger signal to pass through based on the bias
setting of an offset pot.

I own a Doe. MAQ 16/3.  Great unit.  There are two things I wish it did
though that it doesn't.  Wish I could drive it from an external analog
trigger.  Can't do that.  I can drive the rest of my patch from the MAQ's
internal trigger, but VC of periodicity at that point suffers. Another thing
it doesn't have is separate pulse outs for each of the steps.  This is
undoubtedly because each bank can run indepentantly of another, thus
requiring 48 jacks to do this (16 x 3).

There is a way around though which would probably suffice my needs, although
it will not decode separate outs for each steps, it would allow me to turn
certain step's pulses on or off at will: Take the ganged pulse out of any of
the banks and run it through a comparator and use the  bank voltage of one
of the sequencer's banks as an enabling source into the other side of the
comparator.  In this way, I could turn the pulse out off or on at any given
step based on the offset voltage present at that time.

I currently do this using a modified version of Chris McDonald's voltage
adder - I just offset the output of a sequencer bank so the bottom half of
travel is below ground, then use that output to drive a VC switch that is
gating the ganged pulse out of the sequencer bank I am working with.  Steps
above about 1 volt will pass a pulse, those below do not. I would like to do
this though without incorporating the adder, which I need to use all the
time for a billion other reasons.

Anyone have a good starting point for me, the hack designer that I am?

Thanks so much for taking your time with this.

best,

Peter