Omnidirectional Microphone Set This microphone set is a (stereo) pair in an integrated package. It is intended for high quality music recording where a pair of omni mics is appropriate. Installation and Hook-Up The set consists of: 1) Two microphone capsules, which are detachable 2) The cable and battery box package Unscrew the four Phillips head screws to open the cover of the battery box. Find the two snap battery connectors, and connect a 9 volt transistor radio type battery to each. One battery powers one microphone channel, so if one goes dead, the other should still work. Place the two batteries on their sides, adjacent to each other, in the center well of the battery box. They should fit perfectly. Position the wires so they don't get pinched in the cover and replace the cover. Connect the mic capsules to the cables. Note that there is a locking button on the female connector which must be pressed to release the mic capsule when you remove them. On the other side of the battery box, connect the phone plugs to microphone inputs on your tape recorder. When you are not using the mics, remove them or they will drain the batteries. With ordinary use the batteries should last many months. The cables are each about 15 feet long, but should you need a greater distance from your mics, you can use professional type microphone extension cables that use the same style connectors as the mics. Distances up to about a hundred feet should be OK. It is not recommended that extensions be added to the phone plugs on the other side of the box. Tips On Use These mics are intended to be used for high quality music recording in a manner known in the recording industry as A-B, or spaced omni mic placement. The mics are typically spaced apart about 8 feet and approximately equidistant from the performer. They should be somewhat above the performer. The microphones are omnidirectional, that is they pick up sound from ALL directions. They do, however, have a brighter sound directly in front, on axis. You can use this to your advantage by aiming directly when you want a bright sound, and aiming slightly away when you want a smoother sound. If you use the mics outside, you must put a foam windscreen over the mic capsules or the wind will cause a tremendous rumble in the recording. Get any generic windscreen such as Radio Shack's, even if it doesn't quite fit and must be taped on. Some tape recorders have a switch on them called "MIC ATT(enuator)", and may have two or more positions such as " 0dB, -10 dB, or -20dB" This is meant to reduce the strength of the microphone signal before the mic preamp circuitry in the recorder, and it is not the same as turning down the record level controls. Inexperienced recordists, when confronted with a very loud program , will just turn down the record level controls in order to keep the VU meters out of the red area, and still end up with a distorted recording.This is usually NOT the mic overloading, or so called tape saturation from too high a record level, but overload of the mic preamp circuitry in the recorder. The solution is to attenuate, or reduce, the signal going to the mic preamp, and this is what this switch does. Therefore, if you are recording a loud program, and you find that you can barely turn up the record level control and still get too strong a signal in the VU meters, you should attenuate the mic signal with the attenuator switch. It is also possible to modify this mic set (see the technical section). Gary Louie University of Washington School of Music Box 353450 Seattle, WA 98195 206-543-1218 Technical Section The mic set uses a 1/4 inch omnidirectional electret capsule made by Matsushita/Panasonic (WM-063T, available from Digi-Key Electronics). It is set with silicone RTV into the end of a Switchcraft A3M connector. Signal is through pin 2, ground is pin 1. Pin 3 and shell are not connected. The battery box holds the batteries which power the electret capsules, which have internal FET preamp/impedance converters. A capacitor blocks the DC to the tape recorder, and a resistor network attenuates the signal to a nominal microphone level. The entire wiring is electrically unbalanced. Source impedance is about 5K ohms, and should work acceptably with any low impedance mic input. Very low professional inputs may reduce signal level somewhat, but typical consumer mic inputs are about 5 K ohms input impedance and this gives a very normal level. Signal level can be modified in the battery box if desired. Changing the 18K ohm resistor to 30K or 50K will give about 10 or 20 dB less signal.