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CIRCUIT DESCRIPTION
SVRR
(SUPPLY
VOLTAGE
REJECTION
RATIO)
SVRR
is the ratio of change of output voltage and change of
supply voltage when
the supply voltage varies.
It is generally used
to indicate the performance
of IC.
Change of Output Voltage
If the
supply
voltage
of equalizer
is affected
by the power
amplifier, the dynamic crosstalk, S/N and the dynamic range will be
changed
for the worse.
To resolve these problems, the dual power
supply
is used and SVRR
is set to a high value.
SVRR
=
Change
of Supply
Voltage
Zener
3 stage
NE
Comprementary
.
diode
differential
element
(driver stage)
Preventing
High-frequency
for
amplifier
ASO protection
Power
oscillation
compensation
SVRR
circuit
transistor
circuit
circuit
Bias
Protection
circuit
relay
i
ICL input stage —
with FET
Input impedance
—_.—
resistor
ak:
ex
wy
| 10V
8
inner
=z
QO ee
Scosenennaneaaiiinemeensenmnetiioemenesee
dikesze nasa tealiitomenseenaad
Zener
diode
NEF
for SVRR
element
Constant-current
DC PROTECTION
The
DC
potential
at
the
output
terminal
(speaker
terminal)
1s always maintained at zero volt by the positive
and
negative
power
supply
circuits
and
the
differential
amplifier.
However,
if a DC potential appears for a certain
reason, the differential amplifier cannot reduce this poten-
tial to zero
volt and
DC current
flows into the speaker
load which
is therefore destroyed.
Hence, the DC
protec-
tion circuit is installed.
if a DC potential is generated and
cannot
be compensated
by the differential
amplifier,
the
DC protection circuit actuates a relay to separate the load
(speaker) from the load circuit to protect it against destruc-
tion.
Assume
that there
is a DC
potential
at the output
terminal
and cannot
be compensated
by the differential
amplifier.
Then
current
begins to flow through
Re/9
or
Re80 and Ce29 and Ce30 are charged.
If they are posi-
tively charged,
the base
potential
rises at Qe29
which
is
therefore turned on.
When Qe29 Is turned on, the collector
10
i Tre
emmmeiiicomemennedtiamemennesnslitememmennted
OC
protection
cir cuit
potential of Qe29 is lowered and the bias voltige of Qe30
and Qe31
is also lowered.
Thus Qe30 and Oe3l are turned
off and
the relay separates
the load from
the circuit.
If
Ce29
and Ce30 are negatively charged, the dicdes De13 ~
15 are biased
in the forward
direction
to lower
the base
potential
of Qe30..
Thus Qe30
and Oe31
are tuarned off
and the relay also functions to separate the laid
from the
CIFCULE,
This DC protection circuit is devised to pryeent shock
noise which may occur after power switch is o7, When the
power supply circuit is switched on, +Vcc ciurreent flows
through
Re82
and
Ce31.
The relay remainsto
separate
the load until Ce31
is charged up, since the bee
potential
at Qe30
is not raised.
When Ce31
is completly
charged,
Qe30
is turned
on and the relay is reset.
Noshcock
noise
occurs
since this time period (dependent on th ime
con-
stant of Re82 and Ce31) is longer than the cinuj t stabiliz-
ing time after power switch is on.
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