Line Input - Pioneer T-6600/F Service Manual

3. OUTLINE OF ELECTRIC CIRCUIT
Since the
heads
of
Model T-6600
are designed
for
both playback and recording operation,
the
amplifier
circuit is
used
for
playback
and
recording operation
in
forward and
reverse
directions by switching
the amplifier.
Fig.
1
shows
the block
diagram
of
record-
ing/playback
amplifier
and the bias
oscillator in
case
of
the
left-channel playback operation.
PLAYBACK CIRCUIT
1.
The input
signal
picked
up by the
head
(F.R.P.H)
passes
through
the switch (Sz-t)
and
is
amplified
by
the
transistors
(Q1,
Q2).
2
The amplified
signal
which
passes through
the
switches
(Sz-:, Sz-z)
is negatively fed
back
to
the emitter
of
Q1
to
compensating
for the NAB
standard
playback
charac-
teristic.
At
the
same
time, this
signal
is fed
to
transistor Q3 through
the
VOLUME
(VR:)
and
the switch
(Sz-+
).
3. The
signal amplified
by
transistors
Q3
and
Q4 is fed
to
the OUTPUT
terminals.
It
is
also
fed
to
transistor
Q5
to
drive the
LEVEL
METER
(VU) and to the
HEADPHONE
Jack
through the matching transformer.
4.
The
output
levels
at the OUTPUT terminals
and
the output for
headphone can be
con-
trolled
with
the VOLUME
(VRr).
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Sz
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R
RECORDING CIRCUIT
With the FUNCTION TEVER set
to
"REC",
the
switches
(Sz-t
),
(Sz-0)
are
connected
to
the
R side (recording).
1.
The input
signal
which
comes through
the
input
terminals (DIN-type connector
or
LINE
INPUT
terminals) passes through the
switch (Sz-t
)
and is
amplified by
transistors
(Ql,
Q2).
2.
The amplified input
signal is negatively fed
back
to the
emitter of
transistor
Q1,
through
the
switches (Sz-:
, Sz-z\. The .ratio
of
negative feedback
level
is
controlled
by
the
REC VOLUME
for
adjusting the sensitivity
of this
stage.
3. The
signal
which
has passed
through
the
REC VOLUMB and the switch (Sz-+)
is
amplified
by
next
stage
(Q3, Q4) and
is
negatively
fed
back
to
the emitter
of
tran-
sistor
Q3
through
Sz-s
for low
boost.
4.
This
signal
is fed to the
recording
com-
pensator (high boost) amplifier
Q6.
5.
The
signal
for
headphone
output
picked
up
from
Q4
collector and
through transistor
Q5 and the
matching
transformer.
Also
signal
for line output
is
supplied
from
Q4
collector directly.
6.
The
recording
level
is
checked
with
the
LEVEL METER
(VU)
connected
to
the
emitter
circuit of
transistor
Q5.
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Sz-z
REC.
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(VR3)
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R.
EH
Fis.
1
5
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aa
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O
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REC
- PB
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