line amplifier

The line amplifier is shown in Figure 3-5. It will process the phono input circuit, microphone input circuit,
phono and other line input signals without modification after noise reduction and tone processing. The purpose of amplification
is to further increase the signal voltage to match the input sensitivity of the power amplifier input stage. The amplification amount of this stage is 2. The OdBo
    line amplifier consists of two stages of differential circuits and one stage of push-pull output. Field effect arms VI15 and VT16 form a differential input
stage. VrlnVTis is its mirror constant current source. The static operating current of the differential tube is 1.2~1.5mAo. The differential tube
can choose a low-noise junction field effect head such as 2SK30A. The parameters are: 』DSS≥2-3mAoVTi9, VT,zo form a differential
voltage amplification stage, VT21 and VT22 serve as its mirror constant current source. The static operating current of the differential tube is each 2-5mA to obtain a
large dynamic range. VT23 and VT24 form a push-pull For the output circuit, the quiescent current is 10mA, making it work in Class A to improve
its linearity and enhance its load carrying capacity. The output terminal is equipped with AC and DC output modes to adapt to different power amplifier
circuits. Input terminal requirements oC47 and C48 are coupling capacitors for AC output. Good quality non-polar tantalum electrolytic capacitors should be
used in parallel with polypropylene capacitors o Line amplifier The technical indicators are: frequency response is SHz ~ 300kHz (-3cB), harmonic
distortion ≤ 0,01% (1Ⅺ7), input sensitivity is 100mV, input impedance is 47kfl, conversion rate ≥ 44V/*us