Doepfer A-138-c User Manual
doepfer
System A - 100
Polarizing Mixer
A-138c
1. Introduction
Module A-138c is a four channel mixer, that allows to
add or subtract four incoming voltages to the output
signal.
In the middle position of the corresponding control
knob the amplification is zero, i.e. the signal will be
suppressed. Turning the knob counterclockwise the
signal is subtracted from the output sum with increasing
amount. Turning the knob clockwise the signal is ad-
ded to the output sum with increasing amount.
The output control works in the same way, i.e. the
resulting output signal can be additionally attenuated
and/or inverted.
The module is used in the first place to mix control
voltages (e.g. ADSR, LFO). It can be used to mix audio
signals too but there is no difference between adding
and subtracting audio signals unless they have a fixed
phase relationship (e.g. the outputs of a VCO, or the
input and output signal of a VCF). For audio signals
without phase correlation there is no difference between
addition and subtraction for the human ear.
Control In1 works as a DC offset generator (about
-5V...+5V) provided that no patch cord is plugged into
socket Input 1. If this feature is not required it can be
deactivated by removing a jumper on the pc board.
The voltage controlled version of a polarizer is the
module A-133.
1
A-138c
Polarizing Mixer
2. Overview
!
System A - 100
Controls:
1...4 In1 ... In4 polarizing control input 1 ...4
5 Out polarizing control output
1
Inputs / Outputs:
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$
2
3
4
!...$ Input 1 ...4 input 1 ...4
% Output output
5%
2
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