Sony HP-210 - Page 8

Stage/Control
L-f amplifier
Q403
Age circuit
D402, R415,
C426, R428,
C425, R412,
R427, C422,
C421, R401
Audio Amplifier
Function
‘This circuit provides the power
to drive envelope detector D401.
The positive de component at
the cathode of diode D402 is fed
back to the base of Q403, and
from there to Q401 to control
its gain. The time constants of
the age components filter audio
variations out of the agc voltage.
Since the audio-amplifier section contains two
identical amplifier chains, only the left channel will
be described.
MODE switch
82
Preamplifier
Q501, Q502
Equalization
circuit
R505, C502,
R506, C501,
R503
Feedback
circuit
‘R519, C510
Attenuator |
R501, R502,
R507, R508
In the STEREO position of S2,
left and right input signals are
routed to their respective ampli-
fiers. In the MONO position, the
left and right signals are added.
The sum is then fed to both
amplifier channels.
This stage amplifies the small
signal provided by the phono
cartridge, tape recorder, to the
level required at the input of
the power-amplifier section. The
preamplifier uses a complicated
negative-feedback technique that
provides stable operation during
temperature changes, and good
amplification at low-frequencies.
It also applies the audio signal
to the REC OUT jack for
optimum recording.
Phono equalization is achieved
by these filter circuits to obtain
a flat response.
In the any position of the
FUNCTION | switch, feedback
is applied through R519 and
C510 to provide a flat response
in the preamplifier. Be sure to
use replacement components
with the exact same values.
Signal applied to the TAPE or
AUX input jack is attenuated
by these resistors. This allows
the HP-210 to accept signals of
Stage/Control
Channel
separation adj.
R524
BASS control
RV531
TREBLE control
RV532
Loudness circuit
R536, R537,
C535, C536
VOLUME
CONTROL
RV701
Predriver
Q503
Ac balance
adj.
RV541
Phase inverter
Q504
Function
about 400 mV at the TAPE and
250mV at AUX input jack,
and amplify them without
distortion.
This network connects the emit-
ters of preamplifiers Q501 and
Q601 only when the FUNC-
TION switch is set to the FM
position. It provides a form of
negative feedback between the
left and right channels. Any
residual inverted “L” signals in
the “‘R” channel are cancelled
out by the “L” signal from the
“L” channel. The same is true
of residual “R” signals in the
“L” channel.
This control has a range of
+10dB at 100Hz. i
This control has a range of
£10dB at 10kHz.
This compensates for the charac-
teristics of the human ear, whose
tonal response varies according
to the loudness of the sound
being heard. High- and low-
frequency components are in-
creased in ‘inverse proportion
to the VOLUME control setting
by means of R536, R537, C535
and C536.
The level of signal applied to
the power amplifier is deter-
mined by the setting of RV701.
Q503 amplifies the signal to the
level required at the power
output stages.
Controls the bias current of
Q503 and Q504 to the point
where positive and negative half
cycles are simultaneously
clipped when increasing the
input signal.
It also affects the rated output
power.
Stage Q504 has two oppositely-
phased outputs to drive the
- power-output stages in push pull.