How do I change the roll off frequency of the A15HP

Date Updated: December 9, 2010 FAQ #1
How can I change the roll off frequency of the Shure A15HP High Pass filter?

The standard roll off frequency of the A15HP high pass filter is 100 Hz, at a rate of 12 dB per octave. This assumes that output of the A15HP is connected to a load of 1,000 to 2,000 ohms. This is the typical input impedance of a professional microphone mixer. It is possible to change the corner frequency by replacing the two 10 µF capacitors with values as follows:

Capacitor Value

Roll-off frequency

10 µf

100 Hz

3.3 µf

174 Hz

2.2 µf

213 Hz

1.0 µf

316 Hz

You can calculate the capacitor value required for a particular roll-off frequency using the following equation:

(100 / desired roll-off frequency)2 x 10 = new capacitor value(in microfarads)