Unless there is a need for a high pass filter, using a larger
coupling cap won't hurt.
Yes.
Something that's
often forgotten is the series reactance of a cap is a noise
source, just like a series resistance.
Only resistances are a source of brownian noise. Reactances are
not.
So if your coupling
cap is 3dB down at 50Hz working into , say, 1K ohm, it has a noise
contribution at 50HZ same as a 1K resistor.
This is where it takes some discussion.
I take it as a 3.2uF capacitor, that has a reactance of 1Kohm at
50Hz. Its brownian noise contribution is zero.
But the noise current of the active device (FET, BJT, vacuum
tube...) developped across the capacitor will contribute to noise
as much as a 1k resistor at 50Hz, as much as a 10k resistor at
5Hz, as much as a 100R resistor at 500Hz.
Even at 500Hz, it
contributes as much noise as a 100 ohm resistor.
That's partly correct. the contribution of real resistor is brownian
noise + In.Z
The contribution of a reactance is only In.Z. In addition it is
phase-shifted by 90¡ã, so it combines quadratically, not
algebraically. If it is small (<1/10th), it is negligible.
In a mic, there is
a tradeoff between noise and the need to high pass filter thumps
and plosives.
Yes.
The noise
audibility is reduced by the Fletcher-Munson effect, but it's
still there on spectral plots of many mics.
Not only the physiological hearing but mainly the spectral
distribution will make it less perceptible. White noise has less
energy at LF than HF.
I use larger caps
than most engineers, because I think I can hear that LF noise.
I won't debate over teh internet what anybody hears or not. ?
