This product has been discontinued.
It's often necessary to record verbal annotation when videotape documents are created, yet most modern VCRs do not provide a microphone input jack. Camcorders use microphones, but don't permit the use of external video processing devices such as character generators. Enter Decade Engineering's MIKE microphone preamplifier, an elegant solution that was originally designed by customer request. MIKE accepts most microphones, including popular FET electrets, and optionally provides phantom power to eliminate battery replacement concerns. MIKE's frequency response is tailored for maximum speech intelligibility when used with VCRs. MIKE is easy to power, accepting 12~24VDC or 9~16VAC power supplies.
Board dimensions are 2.50(L) x 1.20(W) x 0.70(H). Mounting holes are 0.125" ID. Weight is about 14g or 0.5oz. Operating temperature range is 0~50 degrees C.
MIKE requires +12~24VDC or 9~16VAC (50~60Hz), at less than 10mA.
MIKE requires a 3-pin friction-latch style female plug, Molex part number 22-01-3037, for the microphone input connector, and a 4-pin female plug, Molex part number 22-01-3047, for the power supply and audio output connector. Crimp style contact inserts for these connector bodies are sold separately, as Molex part number 08-55-0102. Other manufacturers, e.g. Amp, offer similar products, including insulation-displacement types that are much quicker to install but require special tooling.
Low-frequency response is rolled off at 300Hz (-3dB), greatly reducing the low-end garbage that commonly afflicts field recordings of speech. High-frequency response is limited only by the VCR used with MIKE, but an optional capacitor may be added to roll off the high end if desired. Audio gain is fixed at +46dB, which puts typical output levels within the VCR's AGC comfort range, but this may also be modified in the field if necessary.
Input & Output Parameters:
Unless modified, MIKE presents a load of about 50K ohms to the microphone. A location is provided on the circuit board for an optional resistor (R6) to reduce input impedance if required. An additional resistor option (R3) is provided, to supply FET electret microphone operating power through the input cable. Clean regulated +5VDC is also available at the input connector.
MIKE's output impedance is about 500 ohms, but the load attached here (VCR audio input) should be 5K ohms or greater. This accommodates virtually all VCRs on the market, even if stereo VCR audio inputs are paralleled.
Product specifications are subject to change without notice. Contact Decade Engineering to confirm current status if any specification is critical to your application.
There's some generally useful information about microphone hookup on Greg Ordy's W8WWW amateur radio page.