AM 334-01-502
24
5. Plug-in Board EF 20 ---Special Effects, Analog Portion
Principles of Operation
Fig. l0 shows the component layout of the EF 20 special
effects board; Fig. 11 is its schematic diagram Refer to Fig.
11 for the following description.
a) Wersivoice
The Wersivoice consists chiefly of the three bucket
brigade chips, 1C2, 4 and 6, which receive their clock
frequencies from three voltage-controlled oscillators
(VCOs) lC1, 3, 5. The control voltages for the VCOs are
generated by the serial analog signal "DAC" via
demultiplexer Ic13.
The audio signal to be processed goes via IC11 to low-
pass filter IC12, which suppresses the higher frequency
signal components. The output signal from the bucket
brigades is filtered anew by IC11 and fed to analog
switch 1C14, which handles the "deep" and "flat"
functions of the Wersivoice.
The processed signal appears at pin 14 of 1C14 The
signal is switched to either pins 3 or pins 4 (edge con-
nector) by 1C15. From there it goes to amplifier AF
12.
b) VCF
The voltage-controlled filter (VCF) receives its input
from pin 6a of the edge connector. 1C15 determines
whether the signal intended for VCF processing is to be
distorted (for E-Guitar, lc8a does the distorting) or go
directly to VCF 1C16. The quality of the VCF is
determined by IC17
Just as for the Wersivoice, the control voltages for the
VCF are generated by 1C13 from the signal "DAC." Ic19
determines whether the VCF is to function as a bandpass
or lowpass filter and whether the VCF works directly or
in conjunction with the Wersivoice.
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