Simplified circuit for bass boost

When RP2 is adjusted to the highest position, point C, the bass is maximized, because C3 is short-circuited at this time , and the circuit fork can be simplified
as Figure 1-61 (a). It can be seen that as the frequency decreases, the capacitive reactance of C4 becomes larger, V2 will increase, and the bass is improved
relative When the frequency drops to a certain level, C can be regarded as an open circuit, because (RP2 +R2)》Ri, so
V2:at;:yl, the improvement is close to the maximum. Since C4 can be regarded as a short circuit for the mid-range and treble areas, the signal transmission ratio for the mid-range and treble
areas is : Vz/Vl≈Rz/(Ri+R2). Figure 1-61(b) is the bass boost characteristic curve , What is the turning frequency of bass lifting = 1/2~rC4R20 The turning frequency of bass from rising to flat is, L1≈1/27tC4. (Ri +R2).