G.R.A.S. 26AH 1/2'' SysCheck Preamplifier with 3 m integrated cable

Freq range: 2.5 Hz - 200 kHz
Noise: 1.8 µV
Gain: -0.35 dB
Special feature: In-situ sensitivity calibration of 1/2" microphone/preamplifier set

Typical application & use

Precision measurements

Low-pressure measurements

General-purpose preamplifiers


All G.R.A.S. microphone preamplifiers are basedon a small ceramic thick-film substrate with a very high input impedance. The ceramic substrate is shielded by a guard ring to minimise the influence of stray capacitance and microphonic interference. The casing is made of stainless steel for maximum strength and durability. The small dimensions of these preamplifiers ensure reliable operation under humid conditions owing to the heat generated by internal power dissipation.


These preamplifiers are compatible with ½-inch microphones as defined in international standard IEC1094 Measurement Microphones, Part 4: Specifications for working standard microphones. The mounting thread (11.7 mm - 60 UNS-2) is compatiblewith other available makes of similar microphone preamplifiers.

Preamplifier Type 26AH is provided with a 3 m high-quality cable terminating with a 7-pinLEMO series 1B plug and has a built-in SysCheck capability. This enables insitu checks of the complete measurement chain from microphone to analyser. The SysCheck technique works by modulating the microphone polarisation voltage.


7-pin LEMO plug 1B male (ext. view)

Frequency range (±0.2 dB) with 18 pF microphone dummy Hz 2.5 to 200 k
Slew rate V/µs 20
Input impedance GΩ // pF 20 // 0.4
Output impedance Ω 75
Output Voltage Swing, max. @ ±14V/+28V power supply Vp 12
Output Voltage Swing, max. @ ±60V/+120V power supply Vp 50
Noise (A-Weighted) max. µV 2.5
Noise (A-Weighted) typ. µV 1.8
Noise (Linear 20 Hz – 20 kHz) max. µV 6
Noise (Linear 20 Hz – 20 kHz) typ. µV 3.5
Gain dB -0.35
Power supply, single V 28 to 120
Power supply, balanced V ±14 to ±60
DC-offset, min., single suppy V 0.5 x Vs - 1
DC-offset, max., single suppy V 0.5 x Vs + 4
DC-offset, balanced supply V -1 to 4
Temperature range, operation °C / °F -30 to 70 / -22 to 158
Temperature range, storage °C / °F -40 to 85 / -40 to 185
Humidity range non condensing % RH 0 to 95
Connector type 7-pin LEMO (FGG.1B.307)
CE/RoHS compliant/WEEE registered Yes / Yes, Yes
Weight g / oz 32.0 / 1.13
Conditions: 23 °C Ambient temperature, ±60V/+120V power supply, 18 pF dummy microphone, 3 m output cable.
G.R.A.S. AA0008 3 m extension cable (7-pin1B LEMO)
G.R.A.S. AA0008 10 m extension cable (7-pin1B LEMO)
G.R.A.S. AA0012 30 m extension cable (7-pin1B LEMO)
G.R.A.S. AA0014 100 m extension cable (7-pin1B LEMO)
G.R.A.S. RA0017 1-inch to ½-inch adaptor for use with G.R.A.S. 1-inch microphones
G.R.A.S. RA0019 ¼-inch to ½-inch adaptor for use withG.R.A.S. ¼-inch microphones