Bass Boost Calculator

This page has a few calculators that will help you to pick optimal component values for the PPA’s bass boost circuit.

These calculators are based on the formulas derived in this Head-Fi thread.

Definitions

ƒc — The frequency at which the boost is +3 dB; the corner frequency of the filter. Below this frequency, the PPA bass boost increases by 6 dB each time you divide the frequency in half, up to the point where the shelving action kicks in.

ƒs — The frequency at which the boost curve is 3 dB below the maximum boost value; the shelving frequency of the filter.

ƒo — Frequency where the gain is half the total boost. Used when boost is 6 dB or less, since ƒc and ƒs cross each other at this point.

I Know What Resistor Values I Will Use, What C7 Will Give Me the ƒc I Want?

This calculator will help you pick a C7 value given the ƒc and the R3, R4 and R7 values. The answer will not be rounded off to a standard value, since different capacitor lines have different standard values.

You may use power notation for the resistors: 120K, 1.0M, etc. The power suffix can be uppercase or lowercase.

Given:

R3:

Ω

R4:

Ω

R7:

Ω

ƒc:

Hz

This calculator requires JavaScript.

The formula for this is:

\(C7 = \frac{k}{2\pi f_c \cdot R7}\)

where

\(k = \sqrt{{A_{bb}} ^ 2 - 2}\)

and

\(A_{bb} = \frac{R7}{R3 + R4} + 1\)

Given All the Component Values, What Filter Characteristics Will I Get?

Given:

R3:

Ω

R4:

Ω

R7:

Ω

C7:

µF

This calculator requires JavaScript.

The formulæ for this are:

\(f_c = \frac{k}{f_\tau}\)

,

\(f_s = \frac{{A_{bb}}}{f_\tau k}\)

and

\(f_o = \frac{\sqrt{{A_{bb}}}}{f_\tau}\)

where

\(f_\tau = 2 \pi \cdot R7 \cdot C7\)