Schematics needed for ....

[Rob]

Well, just make two simple NPN saturation amps..

There is really only one difference between a trigger (short pulse) and gate
amp.

Put a diode, then, on the node after the diode, put a 33k to gnd, then a
cap.

ASCII art that really sux follows now..

gate out ( )---|>|-------]  [-------( ) to base
                              |
                              z
                              z
                              |
                            gnd

This will generate a sharp trigger from an input.. Its a very primitive
differentiator, which only allows a sharp change in voltage to pass and
rejects DC from the entering the base of the transistor.

This design is good for higher gate/trigger voltage, but if you can deal
with 5v, you could use a standard 74xx type buffer amp and just add the same
circuit to its inputs.

Hope this helps

Rob
----- Original Message -----
From: J. Larry Hendry <jlarryh at iquest.net>
To: synth-diy <synth-diy at mailhost.bpa.nl>
Sent: Sunday, December 05, 1999 8:49 PM
Subject: Schematics needed for ....


> I am mostly a lurker here, and most of my synth diy experience has been
> limited to kit construction (PAiA and MOTM) and some limited-scope repair
> work.  However, the deeper I get into modular, the more I find myself
> wanting to do things on my own.  This list has been a great source of
> information, and I appreciate the open sharing that goes on in spite of
how
> recently some of that sharing has been abused by commercial application.
>
> I want to build a circuit that will generate a gate and trigger
combination
> from a switch closure.  I could settle for a gate only, but would prefer
> both.  It seems like this should be simple enough, and I am willing to
> tweak to get the exact voltages I am looking for.  However, I need a
little
> help getting started.
>
> Can someone point me toward a schematic or suggest were I might search to
> find one that would get me in the ballpark for this function?
>
> I have two separate projects for alternate controllers to use with my
> modular that would make use of this circuit.
>
> The first is a Tannerin style controller that is being built for me that
> will output a simple linear CV as the control is moved across the top
> surface.  I want to add a switch that allows me to re-trigger envelopes
(or
> whatever) as I slide this thing around.  I am also going to add a Theremin
> style left side antenna for CV output (Based on the T-max schematics).  I
> think it would be really cool to have this auxiliary CV available for
> opening filters or various modulation uses.  So, the right hand would
slide
> the oscillator CV around and perhaps tap gates with the thumb while the
> left had was free for other expressive elements.
>
> Project 2 is just a plain old joystick with the button on the end.  I have
> a quite nice one that I want to build into a panel in my set up to output
> control voltages based on X and Y axis.  I  thought it would be quite cool
> to have the button generate a gate or gate/trigger when depressed.  The CV
> part is easy.  But again, I need help getting started on the gate/trigger
> circuit.
>
> Thanks as always for this forum and the usually high level of respect
given
> to all who participate.
>
> Larry Hendry
>
>