Camcorder Mic Adapters

Microphone Adapters for consumer camcorders

What value should I use for the capacitor?

MONO Balanced XLR mic to Stereo Camcorder mic in (1/8 inch mini-phone)

This circuit will feed the LEFT CHANNEL ONLY on the camcorder
Capacitor C2 blocks DC power supplied by camcorder for consumer electret condenser mics.
This capacitor can be installed in the shell of the XLR connector.
Camcorder (right side) shows internal power insertion resistors and DC blocking capacitors.
This can also be done with a "mono" (2-circuit) mini-phone plug.

MONO Balanced XLR mic to Stereo Camcorder mic in (1/8 inch mini-phone)

This circuit will feed the BOTH CHANNELS on the camcorder
Capacitor C2 blocks DC power supplied by camcorder for consumer electret condenser mics.
The capacitor can be installed in the shell of the XLR connector.
Camcorder (right side) shows internal power insertion resistors and DC blocking capacitors.

STEREO Balanced XLR mic to Stereo Camcorder mic in (1/8 inch mini-phone)

Capacitors C1 & C2 block DC power supplied by camcorder for consumer electret condenser mics.
These capacitors can be installed in the shells of the XLR connectors.
Camcorder (right side) shows internal power insertion resistors and DC blocking capacitors.

What value should I use for the capacitor(s)?

Short answer:
something between 1 to 5 microfarads @ 5v.

Long answer:
The capacitor value depends on:
1) The input impedance of the camcorder
2) The low-frequency rolloff (3dB down frequency)

I use this web page...
http://www.opamplabs.com/rfc.htm
to calculate the capacitor value.

For example, if your camcorder input impedance is 2500 ohms and you want frequency response down to 20 Hz, then you would use a 3.18 microfarad capacitor.

You can type in any two numbers and it will solve for the third. For example, if I still assume 2500 ohms input impedance, and plug in 1 microfarad, then I get a 63.6 Hz 3dB down point.

Note that most camcorders don't have published specifications for mic input impedance.

Note also that you may not want a lot of low frequency response unless you are recording flamenco dancers on a hardwood floor or a steam engine, or a pipe organ. Most low frequency sound out there is undesirable noise (at least for the purposes of video!)

Any capacitor which has the required capacitance and voltage values can be used. If you want to put the cap inside the XLR connector shell, you will need a pretty small one.

Surface-mount capacitors of appropriate capacitance and voltage values are now readily available, but their tiny size means that you must be careful handling and soldering to them.

rcrowley.com Mic Adapters for Camcorders

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