Convention Paper
Professional Line Output Level Electret Microphone for Public-Address Use
AES Convention 62 · Paper 1455 · March 1979
Abstract
The electret technology has already been described in several papers. This paper will show how an electronic symmetrical line output level electret microphone can be designed for public-address use. Because of the small dimensions of an electret unidirectional microphone insert the proper acoustical parameters, such as suitable frequency-response and constant front-to-random index throughout the useful frequency band, can easily be obtained. Application of recently available electronic circuitry and components in the built-in line-output level amplifier and limiter enable transmission over unscreened cable up to 1 km length. This microphone is compatible with any moving-coil or other electret microphone. Because of the integration of transducer and electronics, an excellent S/N ratio can be obtained. Th'power for the electronics being supplied over separate wires by the power amplifier the microphone requires no built-in batteries. Its line amplifier can drive either a power amplifier up to rated output or a 600 Ohm line. The philosophy of this design will be explained in this paper.
