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These G.R.A.S. microphone preamplifiers are small robust units optimised for acoustical measurements with condenser microphones.
Connections to preamplifiers are most often made via a 7-pin LEMO series 1B connector; unless its a CCP* Preamplifier. These connectors (see diagram on the right) are widely used, ensuring compatibility with a wide range of power supplies, analyzers etc.
All these preamplifiers are compatible with measurement microphones as defined in the international standard IEC 1094 ”Measurement Microphones, Part 4: Specifications for working standard micro-phones”.
All G.R.A.S. preamplifiers are based on a small ceramic substrate thickfilm precision amplifier with very high input impedance. The casings are made of stainless steel for maximum strength and durability with minimum sensitivity to vibration and microphonics.
G.R.A.S. microphone preamplifiers will work within their specifications up to a temperature of 70°C. They can, however, be used safely at temperatures up to 120°C without damage. The only effect of elevated temperatures is a slight increase in the self-noise of the preamplifier. This will affect the lower limit of the dynamic range of the microphone/preamplifier combination and limit its ability to measure very low sound pressure levels.
However, for a high-temperature application, such as measuring sound close to a diesel engine, this would normally not be a problem because of sufficiently high sound pressure levels.
* Constant Current Power.
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