<EW
X-5 BASS
SYSTEM
PEDALS
&
BASS
TO
LOWER
MANUAL
INTRODUCTION
The new X-5 Bass System
supplies bass
tones for 13 pedals at
both
16'
and
8'
pitches, as well as bass tones for twenty
lower manual keys. Figure 1
shows
the
relative ranges of bass tones
employed
by the
lower
manual and
pedals. In
manual bass the
system operates in a
low select manner because of the
action
of 3 priority-encoder ICs.
In pedal
bass
mode the system operates high select
because of the wiring of the pedal
Obly.
The heart of the X-5 Bass System is
the
Bass Generator Board (223-35386).
This
board contains 10 basic sections.
These sections are:
1)
A diode ladder matrix
2) A priority encoder stage
3) An
inverter NOR gate stage
4) A latch
stage
5) A
channel data selector stage
(Multiplexer)
6) A
divider stage
7)
Octave select gates
8)
Envelope gates
9) A
Mute filter
10) An
amplifier stage
The?t
Ti
t
stages
interact to provide all the
features that
are associated with bass
on the X-5.
Figure 2 in the back of this
booklet
demonstrates how these basic
stages fit
together in a functional
block
Notice in
Figure 2 that the
keying
inputs from the
pedals or lower
manual
are applied to J503,
J504, and J505
and
the diode
matrix. The selected
keying
inputs
are logic 1 (ground)
levels which
are received by the matrix
and are sent
to the
appropriate data (D1-D7)
inputs
of the priority
encoder stage (ICs 1, 2
and 3).
^
The
priority encoder
ICs encode the
5 highest
priority input (D7-D0) to
a
3
bit
**
bi
code. This code is
released at the
-
Q2,
Ql, and 00 outputs.
The encoders
also
release inhibit/ enable
information
at
their
Gs
outputs. This
inhibit/ enable
information
is used to disable or
enable
the data selector ICs later on
in the
keying
process.
Both
the note select code and the
inhibit/enable code are
sent to the
inverter stages of IC7 and transistors
Q1-Q2 respectively. The NOR gates
within IC 7 invert the note select
data,
and transistors Ql
and Q2 invert the
inhibit /enable information.
Following
inversion, the two codes
travel
to the latch stage. Latching is
accomplished
by ICs
8, 9,
10, and 11
which
are
quad NAND
gates
wired
as
flip-flops. The latches
receive the data
from
the inverters, re-invert the infor-
mation, memorize the information, and
then apply the information to the note
select (A, B, C) and disable (D) inputs of
the data selector ICs 4, 5 and 6.
The combination
of note select and
inhibit data at ICs 4. 5, and 6, allows a
specific bass frequency (from J501,
J502,
or
J503)
to pass through the
appropriate data
selector IC
and
reach
the Z output
buss. The selected signal
enters a buffer stage and
flows
to the
divider stage of IC15.
..
Figure 2 demonstrates
that IC15,
a
dual D
flip-flop generates the low bass,
and
medium bass frequencies. The
output
signal from
the data
selector ICs
clocks IC15 and also feeds
IC12
as
the
high bass signal.
The high bass,
medium bass, and low bass
signals then
enter IC12, the bass select gates.
The
combinations of inputs at the
bass
select gates from the key down
data buss (S), the bass elect data bass
(R),
and the
1678'
stop
determine
which combination of bass frequencies
pass
through the bass select gates of
IC12 and enter the envelope gates
of
IC14.
During times of
manual or pedal
down, the key
down
data
buss applies
an input to
the D section of IC14. The
NAND gate
activates transistor
Q4,
and
Q4,
in
turn, sends a gating pulse to the
3 envelope
NAND gates of 1C14 A, B,
and C.
The result of this operation is the
gating of the
appropriate bass tones
through
the envelope gates to the RC
mute filter.
If String Bass is selected,
the. envelope
generator
continues to
function after the key or pedal is
released and a sustain
effect occurs.
At the
RC
mute
filter
transistors 08
and
Q9
normally permit maximum
bass
signal to reach amplifier Q10. When the
mute
tab
is activated, transistors
Q9
and
QIO conduct
and
shunt
a
portion
of
the bass signal away from QIO. The
result of the mute operation is a
significant drop in volume of the bass
tones.
The output
signal of the mute filter
feeds
amplifier QIO, travels through the
bass
level
adjust
potentiometer, and
leaves the
Bass Generator Board
at J507
pin
1. After leaving
the
Bass Generator
Board, the bass signal
travels
to the
organ preamp
where it mixes with
signals from other systems of the organ.
GENERATION OF BASS TONES
(EXAMPLES)
As
stated previously, the Bass
Gener-
ator Board
contains 10 basic
sections.
These
sections interact
to produce all
base tones
required by the organ.
The
operation
of the Board, however,
is not
consistent
over the entire pedal
and
manual
frequency ranges. The
board
can operate in
five different modes, and
the selected
pedal or lower manual keys
in the
16'
or
8'
settings determine the
appropriate
mode. The following list
defines the conditions which
set the
Bass Generator Board
for the various
modes of operation:
Mode #li The
pressing of a pedal
1-5
(low C through
E) when the
bass stop
is
set for
16*.
Mode #2i The pressing
of a pedal
6-13
(F through high C)
when the
bass stop is set
for
16'.
Mode #3i
The pressing of a pedal
1-5
when the bass stop is set
for
8'.
Mode H: The pressing of a pedal
6-13
when the bass stop is
set for
8'.
Mode ftS: The pressing of a lower
manual key
1-20
when the
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