Dear mic experts,
I'm trying to design a discrete amplifier for an electret capsule and have quite a technical question that is puzzling me. The device is a PUI AOM-5024L.
I encountered the possibility of driving the capsule with a (common-emitter) preamp that has an input impedance much lower than the capsule itself. Say the electret has 2.2k out-Z, while the preamp would have 850 in-Z. I know this will result in huge attenuation, but this is not a problem for me but rather an advantage. It means lower resistance (noise) on the preamp's first stage bias and the possibility of bypassing later stages for capturing loud environments¨Cwhich is problematic with this very sensitive capsule. However, I don't know if loading the electret with a much lower impedance will affect ie. the capsule's frequency response (flatness) or its maximum headroom. Since there is a JFET buffer in between inside the cartridge, I tend to think that the JFET would absorb the load or separate and only attenuation would be affected, but I'm not sure about it.
Has anyone for instance seen or done frequency and/or headroom measurements on (JFET) electrets at different loading impedances? Or have any theoretical clues about this? I've read opinions that overloaded mics tend to sound bassy, lack highs or sound 'obscure' whatever that means, but might be that those comments refer to passive mics.
All opinions are more than welcome.
Best regards,
Domingo
