# Change the high pass filter in a microphone

Discussion in 'The Projects Forum' started by TaperChuck, Nov 17, 2013.

1. ### TaperChuck Thread Starter New Member

Nov 8, 2013
3
0
I'd like to change the high pass filter frequency in this microphone. Is there an easy way to make the high pass filter set at 50 Hz and with a 3 dB/ octave rolloff? As is, I believe it's around 80-100 Hz at 6 dB/ octave.

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2. ### TaperChuck Thread Starter New Member

Nov 8, 2013
3
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I hoped someone would be able to help me with this project.

It looks to me like switch K1 when open uses R21 (10M) to leave the roll-off flat. When the switch is closed R16 (300K) is put in parallel with R21 and the resistance is lowered to 291K to form a high pass filter.

I just don't understand what other components are involved to form the high pass filter though. Typically a high pass circuit has a resistor that is tied to ground and the signal is run though a capacitor to form the high pass circuit.

That doesn't seem to be the case here. ??? I'd appreciate any input that will help me understand this circuit and how to implement a -3db/octave high pass filter at around 50 Hz.

3. ### shteii01 AAC Fanatic!

Feb 19, 2010
4,452
707
A series RC circuit forms a high pass filter, the output of the filter is taken at the resistor in the form of voltage across the resistor.

Cutoff Frequency=1/(2*pi*R*C) in Hz

4. ### TaperChuck Thread Starter New Member

Nov 8, 2013
3
0
Yes, thank you. Given the correct component values I can calculate the high pass frequency.

I don't know which components are interacting to form the filter in this circuit.