Signal Processing - Yamaha CS-80 Instruction Manual

and you
suspect
some
control(s)
was accidentally
moved,
don't panic; just
go
to a preset
while
you
check
the panel levers
and
switches.
TIPS
ON AUXILIARY SIGNAL PROCESSING
Phasers, echo boxes, reverbs,
digital
delay
lines,
parametric
equalizers,
fuzz boxes,
wah-wah
pedals,
graphic
equalizers, etc. are
all
auxiliary signal
processing devices that
may
be used with
a
synthesizer.
The
synthesizer
output
is
higher
in
level
than
most
electric guitar
pickups, but
it
can
still
be
plugged
into
many
guitar-type pedals and
boxes
if
the
HIGH/LOW
switch
is
at
LOW
and the
Volume
control
is
set at
a
moderate
level.
On
the
other hand,
it
may
be better to use an external
attenu-
ation
pad to
match
the
level
of the synthesizer out-
put
to
a
high-sensitivity
(low
level)
effects device.
Signal
processing
equipment made
to interface with
studio
equipment can usually be driven directly
from
the synthesizer
output with the
HIGH/LOW
switch
in
HIGH
position.
In all
cases
it is a
good
idea
to
check the
level (sensitivity)
specifications for
the
auxiliary signal
processing unit against the synthesizer
specifications.
Many
of the
sounds you might wish to achieve with
an outboard effects device
can
actually be
achieved
with controls and
circuits
that are built into the
synthesizer.
For example, tremolo, vibrato
and wah-
wah
can
all
be
obtained using the sub
oscillator.
Where
practical,
use the built-in capability of
the synthesizer,
since the
sound
will
be going
through fewer
circuits
and
will
therefore have the lowest noise
and
best
frequency
response.
Many
patches are greatly
enhanced by auxiliary
signal
processing.
The
realism of
"acoustic "
instru-
ment
patches can be very
much
heightened by
using
reverb.
The
synthesizer's External input can afford
some
interesting effects.
To
obtain strange
''vocal"
effects,
plug
in a
source of
a
very pure,
high-frequency sound,
such
as a
10kHz
or
higher
sine
wave
oscillator.*
Then
engage the
VCF
(filter)
on
the sub oscillator,
and add
a
lot of
Resonance
[8
and/or 27 &29]
.
The External
input
is
not
made
for use with guitars or
microphones,
and even
if a
preamplified guitar or
mic
is
used, the
results
could be disappointing.
Some
preamplified
(electric)
instrument outputs
will
produce interesting
results
when
connected to the External input.
*The purer
the sine
wave
fed
to
the externa/ input, the
better-sounding
the result will be.
DIRECT BOX
A
"direct-box"
is
a
type of adapter. In
some
cases,
rather
than connect the
CS-80
directly to
a
mixer, one
could connect the synthesizer
to
an instrument
amp.
The
direct
box would then be used to interface the
instrument amplifier's
speaker output
(guitar
amp,
P.
A.
amp,
etc.)
with the
mic
or
line level
mixer
input,
thus
including the
amplifier's reverb, tremolo, brightness
and
other effects
in
the
mix.
Another
application for
a
direct
box
is
to achieve grounding
isolation
between
an
unbalanced
line level
output and
a
balanced
mic
or
line
level input.
The CS-80 output has
a
low
source
impedance
so
that
it
will drive
a
low impedance (600-ohm)
or high
impedance
input
without
adapters.
The CS-80 output
is
unbalanced,
meaning
that the signal,
which
flows
through
a
single-conductor shielded cable,
is
grounded
on one side (the shield)
and ungrounded on the other
side (the
center conductor). This
arrangement
is
per-
fectly suitable for cables of
up to 3
m
(10')
in
length.
When
a
longer distance separates the
CS-80 output
from
the
mixer
input,
it is
desirable to use
a
balanced
line
rather than an
unbalanced
line
for better rejection
of potential
hum,
noise
and
interference. In a
balanced
line,
the cable shield
is
grounded, but
carries
no audio
signal;
two
center conductors, neither of
which
is
grounded, carry the
signal.
Provided the mixer
input
is
balanced (transformer isolated),
a
balanced
line will be
obtained by connecting
a
direct
box
at
the
CS-80 output.
if
two
or
more CS-80
outputs
are
connected
to
one
mixer,
it is
a
good
idea to use a direct
box on
each
output
so that the
ground
to
all
but one
of
the inputs
can be interrupted
without breaking the
signal
path.
This avoids so called
"ground loops," multiple
grounding
circuits
between
the
mixer and
the
synthesizer that might otherwise introduce
hum.
PAD IN/OUT SWITCH
The
direct
box
illustrated
can be used
in
three ways,
as
indicated below,
and
its
three switches should be
set
as
required.
The ground
switch breaks the
ground
(shield
connection)
in
the
XLR
output,
and should be
set
for
minimum hum. The
Pad drops the signal
level
so
that high
level
outputs do not overdrive lower
level
mixer
inputs.
The
Filter,
which only
works when
the
Pad
is
switched IN,
simulates the high frequency
roil
off of a
typical guitar
amp's speaker. Since clipping
distortion in a
guitar
amp
often creates high
frequency
harmonics, the
filter
switch, by lowering high
frequency
response, also cuts distortion.
47
Assemble
the unit
in a
small
metal mini-box, and
keep the
phone
jacks isolated
from
the
chassis of the
box. Also keep the
box away from
the chassis
of the
instrument amplifier or any other
grounded
object.
if
you chose
a
transformer other than the
JE-DB-D,
it
should have
similar characteristics:
an
impedance
ratio
of
20k-ohms (primary)
to
1
50-ohms
(secondary), dual
faraday shields, very
low capacitance on the primary
winding,
and
full
audio spectrum response.
A
commercial
direct
box
may
be
purchased, or
a
qualified technician
can
build
one from
the schematic
diagram shown
here.
The
design,
courtesy of
Deane
Jensen (Hollywood, CA),
is
included in this
manual
for the benefit of the synthesizer user,
and does not
represent an
endorsement
by
Yamaha
of the specific
products mentioned. This direct
box
also
works
well
with
electric guitars,
maintaining
good
high
frequency
response because the pickup
is
not loaded.
The JE-DB-D transformer
is
available directly
from:
Jensen Transformers
1617 North
Fuller
Avenue
Hollywood,
CA
90046
(INSULATED BUSHING)
SWITCHCRAFTN-in
(FROM SYNTHESIZE R)[ir
(TO
INSTRUMENT AMPlQ^
INPUT/
BRIDGING
JACKS
+
+
V^
^S^
JENSENS
JE-DB-D
22uf
25V
22uf
25V
1.
T
il
FILTER
SWITCH
Direct
Box Schematic
XLR-3-nC
ID3M)
2-i
(TO
p
MIXER)
OUTPUT
JACK
\
GND
SWITCH