Akai AA-A35 - Description of the Circuit Operation

V.
DESCRIPTION
OF.
THE
CIRCUIT
OPERATION
eee
5-1.
AMPLIFIER
PERFORMANCE
5-1-1
General
Description
(1)
Functions
a)
Input
Selector
Control
This
microcomputers
is
capable
of
controlling
analog
switch
TC9164N
that
serves
as
the
input
selector.
Three
input
systems
that
include
PHONO,
CD,
and
TUNER,
and
two
monitoring
systems
that
include
TAPE
|
and
TAPE
2
may
be
controlled.
b)
Direct
Access
Volume
Control
Reads
voltages
detected
out
of
the
sound-volume
touch
control
through
an
A/D
converter,
and
sets
the
electronic
potentiometer
in
accordance
with
the
read
data.
In
this
process,
any
designated
setting
will
be
reached
from
the
earlier
potentio-
meter
position
by
fading
in
or
out.
c)
Balance
Control
By
setting
various
level
differences
between
Lch
and
Rch
on
the
main
control,
up
to
a
maximum
of
30dB
L-R
level
offsets
may
be
created.
d)
Tone
(BASS/TREBLE)
Control
Operates
the
tone
control
potentiometer
(TC9156P)
in
2dB
steps
up
to
a
maximum
of
+10dB,
and
thereby
performs
as
an
electronically
controlled
tone
circuit.
f)
Acoustic
Pattern
Storage
By
this
function,
stores
in
the
microcomputer
two
patterns
of
the
tone
control
circuit
settings,
and
enables
the
instant
loading
of
either
of
the
stored
patterns.
g)
Volume
Control
Safety
Function.
With
the
touch
contro!
operated
direct
access
sound
volume
system
that
enables
the
instant
setting
of
any
preferred
sound
volume
level,
the
danger
exists
that
the
inadvertent
touch
of
a
higher
position
of
the
control
will
cause
a
sudden
emission
of
unexpectedly
high
sounds
from
speak-
ers.
A
time
lag
measure
in
the
form
of
fade-in’s
has
been
provided
to
enable
coping
with
the
above
danger,
but
as
an
added
and
positive
precau-
tion,
this
safety
function
has
been
added
on
that
suppresses
all
sounds
louder
than
a
level
set
in
advance.
h)
TUNER
Direct
Function
This
function
will
set
the
input
selector
at
TUNER
upon
receiving
data
from
the
microcomputer
(A1007T)
for
the
tuner
that
is
output
as
soon
as
the
tuner
has
been
operated.
PIN NO
©® © © © ©
SINGLE PRESSING
CONTINUOUS
DEPRESSIONS
5-1-2
Key
Input
and
Dynamic
FL
Display
Strobes
Key
inputs
and
FL
displays
are
both
handled
dynam-
ically,
and
their
basic
clock
signals
generated
by
the
ITMR
interrupt
(1,024
Hz)
for
the
output
of
strobe
signals.
msec >|
oe Max re0nsee
R50
RSt
Fig. 5-1
5-1-3.
Acceptance
of
Key
Inputs
sl
zamsec
s0oms 150 150 10 150 150
Fig. 5-2
© Chatterings will be absorbed for 24 msec.
©
Continuous.
depressions
will
be
accepted
first
at
24
msec
after
the
depression
start,
second
at
500
msec
after
the
first,
and
then
at
every
150
msec
thereafter.
e
All
multiple
depressions:
shall
be
inhibited.
Once
a
multiple
depression
is
made,
no
key
inputs
will
be
accepted
until
after
all
of
the
depressed
keys
have
been
released.
5-1-4 Key Processings
(1). [PHONO], [CD]
Sets
the
input
selector
(TC9164N)
for
either
of
the
input
modes
keyed
in,
and
makes
due
indications
for
it.
Nothing,
however,
will
occur
when
the
depressed
key
mode
has
already
been
engaged.
When
either
TAPE
1
or
TAPE
2
has
been
keyed
on,
the
displays
for
a
tape
monitored
input
will
be
flashed
on
and
off
for
10
times
at
a
1/2
duty
and
once
every
second,
to
alert
the
operator
of
the
ongoing
tape
monitoring.
In
addition,
when
serial
data
is
being
transferred
to
the
analog
switch,
the
—_——
SERVICE
MANUAL
AA-A35/L
ON
Or
8