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 are widely used, ensuring compatibility with a wide range of power supplies, analysers 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 thick-film 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 it's 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.
 

Click on images for details:

1/4" Preamplifiers
Type 26AA for Intensity Measurements, preamplifier with 30 cm lightweight cable terminating in a 4-pin LEMO 0B connector	Type 26AC general-purpose preamplifier with an integrated 3 metre lightweight cable terminating in a 7-pin LEMO connector
Type 26AL built-in SysCheck, general-purpose preamplifier with an integrated 3 metre lightweight cable terminating in a 7-pin LEMO connector	Type 26HG infra-sound use, similar to Type 26AC but with 40 GOhm input impedance for low-level noise measurements at very low frequencies
Type 26AB general-purpose preamplifier with integrated 7-pin LEMO connector. Adapter, AF0008, included for use with G.R.AS. 1/2" microph. No Cable	Type 26AN for using insert-voltage technique to determine the open-circuit sensitivity of microphones, with integrated 7-pin LEMO connector
Type 26TC built-in TEDS*, preamplifier with an integrated 3 metre lightweight cable terminating in a 7-pin LEMO connector * Transducer Electronic Data Sheet as proposed by IEEE-P1451.4
SHORT 1/4" Preamplifiers
Type 26AS for acoustic measurements using condenser microphones, a small robust unit short enough for use in confined spaces	Type 26AR for acoustic measurements using condenser microphones, very low inherent-noise, wide dynamic range, freq. response: <2 Hz - 200+ kHz
1/4" CCP (Constant Current Power) Preamplifiers
Type 26CB for use with prepolarised microphones, integrated with a Microdot connector, delivered with 3 m Microdot-BNC cable	Type 26CC similar to Type 26CB but with an integrated SMB connector which allows it to be used directly on G.R.A.S. Array Modules PR0001 and PR0002
Type 26CG for for measurements at very low frequencies (infra-sound), below 1 Hz, very wide bandwidth + low noise level	Type 26CS very a very small preamplifier, integrated with a Microdot connector and delivered with a 3 m Microdot-BNC cable
1/2" Preamplifiers
Type 26AK general-purpose preamplifier with an integrated 7-pin LEMO connector     NOTE: cable not included	Type 26AJ built-in SysCheck, general-purpose preamplifier with an integrated 7-pin LEMO connector     NOTE: cable not included
Type 26AM general-purpose preamplifier with an integrated 3 metre lightweight cable terminating in a 7-pin LEMO connector	Type 26AH built-in SysCheck, general-purpose preamplifier with an integrated 3 metre lightweight cable terminating in a 7-pin LEMO connector
Type 26AG for using insert-voltage technique to determine the open-circuit sensitivity of microphones, with integrated 7-pin LEMO connector	Type 26TK built-in TEDS*, preamplifier with an integrated 7-pin LEMO connector     NOTE: cable not included * Transducer Electronic Data Sheet as proposed by IEEE-P1451.4
1/2" CCP (Constant Current Power) Preamplifier
Type 26CA general-purpose preamplifier with standard BNC output connector, used with prepolarised microphones     NOTE: cable not included
1/2" CCP (Constant Current Power) Preamplifier with Gain and Filters
Type 26CF general-purpose preamplifier with standard BNC output connector, used with prepolarised microphones, two flush-mounted switches to select combinations of gain and filtering     NOTE: cable not included

Other G.R.A.S. Sound and Vibration products

• Microphones
• TEDS Microphones
• Power Modules
• Intensity microphones and calibrators
• Intensity Probes
• Pistonphones and Calibration equipment
• Telephone test head
• KEMAR Manikins - Types 45BM and 45BA
• Artificial ears, ear & mouth simulators
• Accessories
• Handset Positioning System - Type 45EA