It sepends on the actual input impedance of the mic preamp.
For a typical 2kohm input impedance, the capacitor should be 1.15uF for 70Hz cut-off.
The actual response would be first-order, i.e. only 6dB/octave.
Much less efficient than any active high-pass filter in the preamp.
The actual effective resistance for LF roll-off is 1k5 (input Z of the preamp) + Zo (of the mike)? So a much smaller capacitor is needed for a 70Hz cut-off.
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But Zo of the mike(s) varies a lot so, like Jerry, I wouldn't use this to set the LF limit but only to get rid of subsonic noise.
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Much of this is on page 2 of the latest version of SimpleP48.pdf? dtd. 29sep24
