Transistor attenuation--feedback tone circuit

Figure 4-11 is an attenuation-feedback tone control circuit composed of transistors
. In addition to conventional high and low bass control
, balance control, and equal loudness volume control, this circuit also has functions such as subwoofer control and presence
control. In order to improve the transient characteristics of the entire tone system and reduce distortion,
this circuit uses a higher operating voltage, ±24V power supply voltage. In the circuit structure
, a differential circuit with excellent performance is used as the amplification circuit, so that the signal-to-noise ratio and
dynamic range of the circuit reach a high technical level.
    In the circuit, H and A are the front-stage volume control potentiometers. It cooperates with the equal-loudness
volume control potentiometer brush P7 of the subsequent stage to obtain better loudness compensation effect
while improving the over-excitation capability of the input stage and improving Playback signal-to-noise ratio.
    After the signal from the input stage is attenuated by RPi, it
undergoes impedance transformation through the emitter output device composed of VTi, and then enters the NF type tone circuit for processing. Pin 2
is the presence control potentiometer, which can control the frequency of 500~2000Hz. The signal within the surrounding area is boosted or attenuated by 6^f8dB, which can be used to control
the atmosphere of the scene and increase the sense of presence. RP3 is a subwoofer control potentiometer. It is different from ordinary bass controllers in
that its starting control frequency turning point is lower, about 100Hz. Therefore, when playing dynamic music, the bass performance is
soft yet powerful.
    After the feedback tone control circuit, there is a set of straightened attenuation treble and bass control circuits . RP4 is a bass
control potentiometer. It can better control the frequency response characteristics of low-frequency and mid-low frequency bands in cooperation with the subwoofer control potentiometer RP3
. RPs is the treble control potentiometer . Proper use of this controller can effectively improve the clarity of your program.