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

Freq range: 2.5 Hz - 200 kHz
Noise: 1.8 µV
Gain: -0.25 dB
Special feature: General purpose

Typical application & use

Precision measurements

Low-pressure measurements

General-purpose preamplifiers


All G.R.A.S. microphone preamplifiers are based on 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 the 26AM preamplifier ensures reliable operation under humid conditions owing to the heat generated by internal power dissipation. 


The 26AM preamplifier is 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.

26AM is provided with a 3 m high-quality cable terminating with a 7-pinLEMO series 1B plug.


7-pin LEMO 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 10
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
High-pass filter @3dB cut-off Hz TBD
Gain dB -0.25
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
Humidity coefficient @250 Hz dB/% RH TBD
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.

Low frequency response for various microphone capacities

Max. RMS output signal for various cable loads with 120 V supply

G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.

Optional items

G.R.A.S. AA0020-CL

Customized Length LEMO 7-pin - LEMO 7-pin Cable

G.R.A.S. AL0008

1/2" Microphone Holder, POM

G.R.A.S. AL0012

1/2" Microphone Holder, Stainless Steel

G.R.A.S. AL0005

Swivel head

G.R.A.S. AL0006


G.R.A.S. RA0019

Adapter for 1/4" microphone and 1/2" preamplifier

G.R.A.S. RA0073

Adapter for 1" microphone and 1/2" preamplifier

G.R.A.S. RA0190

Right-angled (90º) Adapter for 1/2" Microphone and 1/2" Preamplifier

G.R.A.S. RA0016

20 dB Attenuator for externally polarized 1/2" microphones

G.R.A.S. RA0062

20 pF Preamplifier-input Adapter for 1/2" preamplifiers

G.R.A.S. 12AA

2-Channel Power Module with gain, filters and SysCheck generator

G.R.A.S. 12AQ

2-Channel Universal Power Module with signal conditioning and PC interface

 G.R.A.S. Sound & Vibration reserves the right to change specifications and accessories without notice.