Modding mic input to take active output

[cyberfish]

It would be nice if I can get a sanity check from audio-savvy people for a mod I'm thinking about doing.

So I am planning to get a camcorder that has an internal omni-directional (presumably electret) microphone, but I want to feed it audio from an external active source (~standard 1Vpp?).

From my research, it looks like typical electret microphone circuits looks like this -
http://en.wikipedia.org/wiki/File:Electret_condenser_microphone_schematic.png
where the microphone is more or less a current source and the drop across the biasing resistor is AC coupled to the input.

Does that mean, if I want to drive it with an active source instead (like MP3 player output), I can just remove the biasing resistor to V+? Or should I add some termination?

EDIT: It looks like mic level is much lower than line level. How about a 101:1 (eg. 10kohm:100ohm) divider?

Thanks!

PS. For anyone wondering, this is for recording cockpit video. Ambient sound would just be noise from the engine/propeller, so I want to feed it from the airplane's intercom, so it can record cockpit conversations and ATC comm.

[SeanB]

It will work, but will be noisy. With the values you propose you do not have to bother removing the resistor to the supply, it will have nearly no effect. Place a mono( or stereo if nothing else is available, you are just using one channel anyway) 3.5mm socket with isolated switch to enable the internal mic to be used if the cable is disconnected. Place the divider in the cable or the 3.5mm plug.

[cyberfish]

It will work, but will be noisy. With the values you propose you do not have to bother removing the resistor to the supply, it will have nearly no effect. Place a mono( or stereo if nothing else is available, you are just using one channel anyway) 3.5mm socket with isolated switch to enable the internal mic to be used if the cable is disconnected. Place the divider in the cable or the 3.5mm plug.

Thanks!
I'll give that a try and see how it goes. Would you suggest another resistor values?

[SeanB]

Try the ones you proposed, if it is distorted increase the 10k to 22k, or place another attenuator before it, use 2 10k resistors to make another L attenuator.

[cyberfish]

I ended up just using a series resistor instead, since someone has done the exact same mod on the same camera (I can't seem to find the link anymore...).

Turned out a 33K in series is all it takes. Sounds awesome.