Control Panel - Yamaha DX1 Owner's Manual

CHAPTER
1
DX1 OLTTLINEn-HE
FM
VOICE
GENERATOR
SYSTEM
1-1
DX1 System
Outline
The block diagrem
in
figure
1
roughly
outlines
the DXl system.
It
consists
of
four main sections:
(1)
CONTROL PANEL
(2)
FM
TOIIE
GmERATOR
(3)
DIGITAL
EG
(4)
KEYBOARD
The simplicity
of
the
systeir:
nas oeen made
possible because
it
functions mostly
on
digital principles.
Based
on the
clock
diagram
in figure
1,
we'll roughly describe
each section.
(1)
CONTROL PANEL
Almost
all controls are logic control
switches. Other features on this remarkably
simple panel include
a
graphic LED display,
an alphanumeric LCD display,
a
few linear
controls and controller wheels.
(2)
FM TONE GENERATOR
In
addition
to pitch,
timbre and level
programming capability,
these
sophisticateo
tone
generators are also capable
of
generating noise components like those found
in natural sounds and acoustic instruments.
They offer unprecedented precision
and
versatility
in
voice creation.
(3)
DIGITAL
EG
This system permits programming time-based
variations
of
pitch, timbre and level.
Because
it is
a
digital system,
the EG
curve
can
be
precisely programmed
in
numeric
form.
Further, the digital EG has
8
variable
parameters permitting exceptionally
versatile
EG curve generation,
(4)
KEYBOARD
This
is
a
73-key, 32-note polyphonic
keyboard with three touch functions:
key
velocity sensitivity (initial touch), after
touch, and key individual after touch.
This
Fig.
1.
DXl Digital Synthesizer Design
-5
CONTROL PANEL
FM TONE GENERATOR
Pitch, Timbre, Level
I
I
DIGITAL
EG
Pitch, Timbre,
Level Variation
t
:>
C^
Audio Signal
^
Control
Signal
KEYBOARD
offers greatly expanded expression
capability. Further,
the
keyboard offers
a
precision weighted-return action
for the
most natural overall keyboard response.
1-2
THE FM TONE GENERATOR
The Yamaha FH tone generator permits precise
control over voice pitch, timbre and level.
The following is
a
brief description
of
Fr:
tone generator principles. See Chapter
9
for
a
more technical explanation
of
Fii
tone
generator
theory.
What
is
Fii?
"
FM stands
for
Frequency Modulation,
just as
it
does when used
to describe an "FM"
station
or
radio broaacast.
The term "modulation" means, basically,
to
superimpose
one
signal
on
top
of
another
signal. In other words,
a
signal
of
a
given
pitch may
be
used
to
"modulate"
a
signal
of
another
pitch.
The vibrato effect
is an
example
of a lov7-f
requency signal
(the
vibrato)
modulating
a
high-frequency signal
{the
note
to
which vibrato
is
applied).
In an
FH radio broadcast,
a
"carrier"
—
an
extremely high-frequency radio signal which
can be transmitted via the atmosphere
—
is
used
to "carry" the program material. The
program material "modulates"
the
radio-frequency carrier.
In
the FM tone generator,
the
carrier and
modulator function
as follows:
CARRIER:
determines the level and pitch
of the sound.
MODULATOR:
determines
the
timbre
of
the^
sound,
"
Of
course, the carrier and modulator
frequencies are much closer together
in the
FM tone generator than they are
in an FM
broadcast, and they are both pure sine
waves.
The
2
Main Merits
of FM
In
an FM
broadcast, since the carrier
frequency
is somewhere around
80
million
hertz (cycles) and the music signal which
moaulates
it
contains frequencies which
are
much lower
—
20
Hz to 20,000
Hz, the
music
signal
is
basically unchanged
by
the
carrier.
If
we bring the frequencies
of
the
carrier and modulator much closer together,
however, we begin to generate new signal
components
—
harmonics
of the
modulator
and/or carrier and noise components.
It
is these modulator-carrier
characteristics that we take advantage
of
in
the FM tone generator.
Its first big
benefit
is
that the FH generator
is
capable