Phono equalized input circuit

If you need to add a phono input, Figure 2-87 shows a phono input equalization circuit, which is composed of dual op amp C1458 and RIAA equalization network. This equalization network has +10dB improvement and 10dB
improvement at the two frequency points of 50№ and 2120Hz respectively.
6dB attenuation o In order to ensure a stable working voltage
for     the pre-stage, tone control and phono equalization pre-stage , two sets of electronic filters are composed of VTi, voltage regulator tube VDi and VTz, VI late, etc., which output stable +15v respectively. And a 15v voltage is supplied to Vc (pin 8) and a Vs (pin 4) of the operational amplifier C4558 and TL082.     The switch noise cut-off circuit is composed of VI, island, R, VI Ga, etc., which is used to control whether the negative power supply of pin 4 of s'rK4191 is applied, that is, whether the internal first stage is biased.     When starting up, since the positive voltage rectified by VGA needs to be delayed by R and C4 for about 2 seconds before it is added to pin 6, the negative voltage from pin 9 is first added to pin 6, and the internal switch is cut off. After about 2 seconds After the delay, the rectified positive voltage of VD2 and the negative voltage from pin 9 are superimposed on pin 6, so that pin 6 is at a positive potential, avoiding the startup shock sound. When shutting down, since the voltage on c4 is quickly released through VIGa, the first internal stage is cut off first, avoiding the impact of shutdown noise.     Relays J l and J2 are connected between the tone control stage and the power amplifier input. The composite tube composed of VT3 and VT4 controls the pickup and release of the relay o