Spectral Ring Modulator
Module 7-701 v. 1.0
Copyright © 2014 CHD Elektroservis. All rights reserved.
No part of this publication may be reproduced in any form without the written permission of CHD Elektroservis.
5
Spectral Ring Modulator function is fully four-quadrant multiplication of the analogue signals from
CARR-IN [5] (CARRIER – carrier signal input with f
CARR
frequency) and MOD-IN [6] (MODULATION –
modulation signal input with f
MOD
frequency). The result of this operation are two, so called, side
bands (new frequencies f
CARR
+ f
MOD
and f
CARR
- f
MOD
) and subsequent cancellation of the original
frequencies (f
CARR
and f
MOD
) – see Fig. 3.
Fig.3 – Examples of side bands creation
RING
W = X * Y
"Y"
"X"
"W"
VCO
SINE
130,81 Hz (c)
VCO
SINE
523,25 Hz (c'')
OUT
SINE
392,44 Hz (g' +2 cents)
+
SINE
654,06 Hz (e'' -13 cents)
RING
W = X * Y
"Y"
"X"
"W"
VCO
SINE
440 Hz (a')
LFO
SINE
25,43 Hz
OUT
SINE
414,57 Hz (g#' -3 cents)
+
SINE
465,43 Hz (a#' -3 cents)
3. CONNECTION THE MODULE TO THE SYSTEM
Fig. 4 – Bus board connection
To connect the module, plug carefully the supplied
ribbon cable into the bus socket of your modular
case. The colored marking of the ribbon cable
must be at the bottom of the bus connector!
Failure to check this may result in the module or
case PSU damage! (module is not protected against
permanent incorrect polarity).
The module uses ±12V of the system only (pins Nr.
1 to 10), GATE, CV and +5V signals are not used
(see Fig. 4).
4. OPERATION
Both CARR-IN [5] and MOD-IN [6] inputs can process signals in the frequency range of 0 to 20 kHz
(i.e. DC signals can be processed too). The input level of both signals is controllable by CARRIER [1]
(for CARR-IN [5] input) and MODULATION [2] (for MOD-IN [6] input). Minimal input level for optimal
signal processing is ±2,5 V
PP
(both pots are in the most right position – MAX in that case).
Both ring modulator inputs “X” and “Y” are equipped with limiter (see Fig. 2) – signals with input
levels higher than the multiplier can process are limited. In this case, certain distortion appears that
might be used for another special sound effects. When the signal is limited, the next new harmonic
frequencies are created.
Spectral Ring Modulator module is equipped with two audio signal outputs RING-OUT [7] and MIX-
OUT [8]. Both outputs provide signal with amplitude of max. ±5 V
PP
(accordingly to the front panel
controls settings).
RING-OUT [7] output provides direct output from analogue multiplier (see Fig. 2).
MIX-OUT [8] output provides the mixed signal of analogue multiplier and dry CARR-IN [5] input signal
(see Figr. 2). The “Dry/Wet” signals ratio can be set by MIX [7] potentiometer. In its most left
(CARR) position, MIX-OUT [8] output provides only the dry CARR-IN [5] input signal. In its most right
(RING) position, MIX-OUT [8] output provides only resulting multiplied signal.
