channel seperation

[David Halliday (Volt Computer)]

There are a couple of techniques that Hal Chamberlin covered in his out of
print Musical Applications of Microprocessors. ( he is selling xerox copies
of his book - check the archives for the info )

Basically, starting from left to right on the ribbon, put your low level (
inputs ) audio signals, then a ground wire, your high level audio signals (
outputs ), then the main electrical ground ( several wires ) your plus and
minus 15 volts, then your plus five volts ( this will be for digital gates
and lighting LEDs and will have more noise on it ) and then another ground
and then your gates and triggers.

Since you will have a lot of connectors in this cable, you might take a
second look at using two ribbons - this will let you keep the power on one
part of the board and the signals on another - much better...

Also, something that Chamberlin discussed was to use the summing points of
the input amplifiers to minimize crosstalk.

Normal mix circuit:

--/\/\/\/\----+
              |
--/\/\/\/\----+----- (to inverting input of opamp
              |
--/\/\/\/\----+

ribbon cable circuit:
--/\/\/\/\----(rc)
              (rc)
--/\/\/\/\----(rc)
              (rc)
--/\/\/\/\----(rc)
              (rc)
              (rc)
              (rc)
              (rc)----- (to inverting input of opamp

This way, the voltage on the ribbon cable is held at zero by the op-amp, the
signal is converted to a current.  The only problem is that your connectors
have to be good otherwise you can get noise and uneven levels.



-----Original Message-----
From: Maarten Halmans [mailto:halmans at globalxs.nl]
Sent: Tuesday, October 06, 1998 12:37 PM
To: Synth-diy
Subject: channel seperation


Hi,

I want to build a modular which is partly hardwired. I want to use a
flat cable to connect the modules to the power supply. The flat cable
will also provide some modules with cv, gate and some audio signals. How
can I prevent interference between the trigger and audio signals without
using extra cables?

Maarten Halmans