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This IC is developed for the low frequency high gain amplifier, of which the withstand voltage is higher enabling the
power supply voltage to increase and then the dynamic range is significantly extended. It is also manufactured taking
the advantage of PCT system (Perfect Crystal Device Technology) which lessens the noise. In addition, the gain of the
first stage is increased as the load resistance of Q1 is made higher and also the noise in the next stage and on is limitted
to the minimum. Therefore, the overall noise through the whole circuit is fully reduced.
The negative feedback block connected between the PIN 6 and 3 works to determine the frequency characteristic and
gain of this amplifier. In this circuit is employed the parallel CR circuit to obtain RIAA curve characteristic but if the
pure resistor is used instead for this circuit, this equalizer also serves as flat amplifier.
3. TONE CONTROL UNIT
The tone control unit is consisted of level controller, tone control amplifier and tone controller. The level controller
comprises the balance control and volume control. As to the balance control of this set, MN type curve rotary variable
resistor is employed. (See Fig. 7.)
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Rotation (degree)
Fig. 7 Balance/Volume
In the tone control amplifier is applied the same IC as that for the equalizer amplifier described in the item 3
"EQUALIZER AMPLIFIER".
Their circuits are the same in basic structure but in the circuit of tone control amplifier is used pure resistor instead of
the negative feedback block as in Fig. 6 to assure a flat frequency response characteristic. Since the tone control circuit
herein is the CR type one which is conventionally employed, the explanation for it is omitted
300°
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