The biggest feature of this circuit is to improve the bass effect as much as possible, attenuate the medium and high notes, and satisfy friends who like the heavy bass effect.

Frequency selective resonant amplifier

Transistors Q02, C 12, C 13 and R32 form an independent (medium and high frequency band) frequency selective resonant amplifier, where C 13 is an AC feedback resonant capacitor and R32 is an AC feedback resistor. (C 13 and E32 form a series resonant circuit, which can change the capacity of C 13. )

Bass frequency signal amplification

When the frequency of the audio signal input from C 12 is close to or consistent with the series resonance frequency of C 13 and R32, Q02 has the strongest amplification ability and the largest absorption and attenuation of this frequency signal, so the amplification of the bass frequency signal of the audio signal through the amplifier U3B/TL064 is relatively improved, and the listening effect is satisfied.

High frequency band compensation

Similarly, the compensation of high frequency band is completed by the next independent circuit.