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IC21 (HC139) decodes the signals from sound source
addresses RA17 and RA18, and inputs them to
sound source ROM chip enable. IC20 (HC138)
decodes the signals from sound source addresses
RA1S to RA18 and forms the ROM card (circuit board
KLM-6008) select signal.
GATE ARRAY sound volume data (REF 0 to 9) are
D/A converted by ladder-type resistor RA25 (IC33-
HC4050 causes only the data from REF 4 to 9 to pass
through a buffer).
IC34 (/*PC624C) multiplies the D/A converted sound
volume data by the sound source data (RD 0 to 7) and
D/A convert the result.
IC36 (HC4051) takes the signal D/A converted by
IC34 (/iPD624C) and output it at the L, R fixed level
determined by the GATE ARRAY channel output (CH
A to C). In addition, IC35 (HC4051) outputs to MULTI
OUT 1 to 6 and the metronome as determined by the
channel output (CH A to C).
Multiplexer output (L,
to 6,
metronome) is fed to an LPF which removes the
25.64 KHz sampling clock signal and outputs the
■Noise reduction
The signal is double half wave rectified by IC26
(NJM072D). Then the sound volume values are con
verted into DC voltage values, and current output is
performed by the pair transistor Q21 (2SA1239).
IC25 (NJM13600) operates as an LPF whose fre
quency range expands from the low region to the
high region depending on the magnitude of the
volume that is input.
■Headphone amplifier
Headphone can be driven by IC27 (NJM4556).
■Bias circuit
After the power is turned ON, this circuit prevents a
clicking sound when the No.1 sound of the GATE AR
RAY is emitted, and applies a bias voltage to the
multiplexer output.
The LCD module displays characters under control of
CPU ports PA 0 to 7 and PB 4 to 7.
■Analogue demultiplexer
This consists of IC3 and IC8 (4051), and sends the
dynamic value of instruction KEY A to N determined
by port A to the CPU. IC1 (NJM 072) is used to hold a
fixed time from the time the dynamic value is input
until the CPU comes to reading.
Port A data are latched by IC2 (HC374) and light the
corresponding LED.
■KEY matrix
Key scanning is done for ports PA 0 to 6, and data for
the key that is pressed are read into the CPU. In addi
tion, Q1 to Q14 come ON when the corresponding in
struction KEY is pressed, forming an alternative to an
electrical switch.
■Instruction keys
Each instruction key employs a switch with a 2 con
tact structure. A dynamic value is produced from the
time difference between the 2 contacts, by the
74HC02 circuit. That dynamic value is input into IC3
and IC8 (4051). At the same time, the information that
the key was pressed passes through transistor Q1 to
Q14 and is output into the key matrix.
a The TAPE OUT (PH1) output level can be varied
using switch 1—2.
b The metronome sound is output at METRO (PH3).
If a jack is not plugged in here, the output goes to
c The polarity of the TRIG output can be changed by
switch 1-3.
d Switch 1-4 is the memory protect switch.
e The LCD contrast can be adjusted by VR1 (10K).
f The signal input by TAPE IN (PH2) is converted tc
the level set by switch 1-1; then it is converted intc
a waveform that the CPU can read by the circuitry
of IC1 (4558).
KUVI-6022 (VOL circuit board)
a Potentiometers VR L and R determine jack outputs
L and R/MONO, and the PHONE sound volume.
b The power supply voltage is voltage-divided by the
DATA SLIDER, and the resulting value is input to
CPU analogue port AN1.
c AUDIO IN can vary the volume of the AUDIO IN in
Scan by Manual Manor


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