Teac C-1 User Manual

AMPLIFIER SECTION
4-2 PLAYBACK LINE AMPLIFIER
The
playback
line
amplifier
consists
of
two
OPE
amplifier
stages.
A
bias
trap
of
100
kHz
and
a
playback
muting
circuit
(Q108)
are
provided
between
stages.
The
muting
effect
is
released
only
while
the
tape
is
running
after
the
pinch
solenoid
operates.
The
playback
line
amplifier
output
has
wide
dynamic
range
and
permits
a
+20
dB
margin
to
facilitate
connection
to
the
Dolby
NR
unit
or
the
dbx
unit.
The
thermister
S5C-34
is
used
to
compensate
for
changes
in
the
playback
head
sensitivity
due
to
changes
in
temperature.
The
resist-
ance
value
of
the
thermister
is
about
30k
ohms
at
an
ambient
temperature
of
25°
C,
it
is
raised
as
the
tempera-
ture
rises
and
vice
versa.
The
playback
head
sensitivity
increases
as
the
temperature
rises
and
vice
versa.
When
the
temperature
rises
and
the
playback
head
sensitivity
in-
creases,
the
playback
head
amplifier
output
level
is
raised.
The
thermister
resistance
falls
at
this
time,
and
lowers
the
input
to
U101.
As
a
result,
the
input
to
U101
is
kept
constant
independent
of
temperature
change.
4-3 DOLBY DECODER
Refer to Section 7.
5. RECORDING AMPLIFIER P.C.B.
Op.
amps
are
used
in
all
circuits
except
for
the
Dolby
encoder.
Every
circuit
is
designed
to
offer
low
distortion
and
wide
dynamic
range.
The
first
stage
has
a
particularly
large
100
dB
dynamic
range
for
sending
signals
to
the
dbx
encoder.
Bias
trap
circuits
(L301,
C304)
and
(L304,
C363)
of
100
kHz
resonance
fraquency
are
provided
at
input
and
output
of
the
recording
amplifier
PCB.
L302,
L303
and
C312
to
C314
comprise
an
MPX
filter
which
removes
the
FM
broadcasting
pilot
signal
(19
kHz)
and
sub-carrier.
A
transistor
switch
is
used
to
change
over
the
equalizer
and
the
recording
level.
Refer
to
the
block
diagram
for
the
relation
of
the
transistor
switch
to
the
EQ
switch
and
the
bias
switch.
The
Dolby
encoder
is
described
in
Section
7.
4-4 PLAYBACK OUTPUT AMPLIFIER
The
playback
output
amplifier
comprises
Q115
to
Q118.
Q115
to
QI17
compose
the
differential
input
current
murror
circuit
described
before.
Unlike
the
playback
head
amplifier
an
FET
differential
amplifier
is
incorporated
in
this
circuit.
The
FET
is
used
to
increase
the
playback
line
amplifier
input
impedance
to
lighten
the
load
on
the
circuit
which
supplies
signals
to
this
amplifier.
The
use
of
FETs
helps
to
suppress
distortion
and
to
in-
crease
the
dynamic
range.
The
muting
transistor
Q119
is
provided
at
the
line
output
terminal
to
effect
muting
to
prevent
unnecessary
click
noise
upon
turning
on
and
off
the
power
switch.
4-5 PHONE AMPLIFIER
The PHONE amplifier comprises a differential amplifier
(Q120, Q121) and a pure complementary push-pull ampli-
fier (Q122 to Q124). A large level margin is required on
the supposition that the output dynamic range will be
80 dB or higher when the dbx system is used.
25

Teac C-1 Specifications

General

Brand	Teac
Model	C-1
Category	Cassette Player
Language	English