Equivalent circuit for bass boost

When RPl is adjusted to point A, C is short-circuited
(1) Only the effect of Vi on Vb is considered, and the effect of Vo on Vb is not considered. The equivalent circuit is shown in Figure 1-80 (a).
Obviously this is a voltage divider. Attenuation circuit, for low audio signal , the capacitive reactance of turtle is large, the impedance of G, RPl.Rl1 branch
is large, and the attenuation of Vi is small, so Vb is large; while for high audio signal C6, the capacitive reactance is small, then Vi Most of them are bypassed
and the attenuation is large, so Vb is small. The result is that high audio frequency is much attenuated than low audio frequency. Relatively speaking, low audio frequency signal
is improved.
    (2) Only consider the effect of Vo on Vh, When the effect of VI on Vb is not considered, the equivalent circuit is shown in Figure 1-1(b)
(flp changes the VQ grounding in Figure 1-80(a) to vi grounding). It can be seen that this is a voltage-dividing negative feedback circuit.
For low-frequency signals, the capacitive impedance is large, the negative feedback is weak, and Vb is less attenuated; while for high-frequency signals, the capacitive impedance is small, the negative feedback is strong, and
"is much attenuated, which relatively improves the low- frequency signal . Integrated input path and The combined effect of the feedback path results
in /V of the bass being boosted when RPi is adjusted to point A; the curve is shown in Figure 1-80 (c).