Modular Synth Panels

On 1/31/09, wjhall11 put forth:
>OK, we're biting <G> - where do we learn about these passive circuits?

It's where most most introductory textbooks on electronics start.
Typically, they begin by describing resistors, capacitors, inductors,
then move onto discrete semiconductors.  At this point, there is
probably enough on the web to get started.

Another approach is to look at active circuits, such as synth modules
and stomp boxes, then realize that the active circuitry is often just
an impedance buffer.  There is often an input buffer stage
such as an op-amp, followed by a passive network, then an active
output stage.  In something like an MOTM modular, the output
impedance of the modules are already low, and the input impedances
are already high, so you can often just put that passive network between
the two modules without adding additional buffer stages.

One thing to look at is passive filter designs.  One can make low
pass, high pass, band pass, and notch filters using only passive
components.  Say you want to change the input of a ring mod from
being AC-coupled to DC-coupled.  The MOTM-110 has a switch, which is
a nice feature, but the 190 doesn't.  Put a large cap between two
jacks and you have a high pass filter.

Want to use an 820 as an envelope follower?  Build a half-wave
rectifier with a diode.

Distortion and waveshaper circuits can also be built using diodes (as
well as LED's, transistors, FET's, etc. acting as diodes) which can
be further developed by adding capacitors and resistors.

A pulse stretcher can be built with a diode followed by a cap going
to ground (provided by the shield of the jack).  As long as it is
going into a high impedance input, you don't need a buffer stage.

If you want to trigger an EG from two different sources, an OR gate
can be built from two diodes.

Anyway, that should give you some ideas.