Bass boost calculatorThe following calculator computes the frequencies and gain of the bass boost effect when enabled, for the given values of R3, R4, Rbb and Cbb. If you're not adding the bass boost feature, this calculator can also be used to compute the total amplifier voltage gain given the values of R3 and R4 (simply set Rbb to 0 and leave Cbb unchanged).
If you are building with a variable bass boost control, set Rbb to the value of the potentiometer, and the calculator will show the results at maximum boost.
For optimum performance, the value of R4 should be set to between 3KΩ and 50KΩ, and then select a value of R3 to achieve the desired baseline gain.
The value of Cbb and R3 should never be set to zero.
The bass boost circuit is a 6dB-per-octave low-pass shelving filter. Bass response increases from the corner frequency down to the shelf frequency and levels off below the shelving frequency. Increasing R4 decreases the corner frequency and increases amp gain. Increasing Rbb decreases the shelf frequency and increases bass boost gain. Increasing Cbb decreases both corner and shelf frequencies.
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