Unpowered Condenser Mics

[Dynamic Mike]

Does a condenser mic actually turn off (as in cease to function entirely) once the phantom power is switched off, or does it actually just generate an unusably small signal? I presume a dynamic mic is technically functioning 24/7 regardless of whether or not it's plugged in, but I wasn't sure if it would be the same for condensers & electrets.

[GaryM]

For a condenser mic, no power = no capacitor plate voltage = no signal. Elecret mics don't require power (though some have integrated pre-amps that do).

[Hugh Robjohns]

All capacitor and electret mics require an impedance converter between the capsule and the output and that is always an active device and needs power. Without power it won't work and they'll be no output. The power could come from an internal battery, or an external power supply unit (as is the case with most valve mics), or phantom power, or plug-in power depending on the design and application of the mic.

In the case of DC polarised capacitor mics, power is also required to charge the capacitive capsule in the first place too.

So no, without power a capacitor or electret mic won't generate any output at all. Dynamics mics do.

Hugh

[Dynamic Mike]

Thanks Gary/Hugh,

I appreciate it was more of an academic question than a practical one, but I just wondered whether it was functional even when the power was turned off. The only electret I've got is battery powered so I always switch that off when I've finished, but I have a sloppy habit of leaving condensers plugged in with the power off.

DM