GRAS 26AC-1 1/4" Standard Preamplifier with Integrated Miniconnector

Freq range: 2.5 Hz - 200 kHz Noise: 1.8 µV Gain: -0.29 dB Special feature: General purpose

Technology

Design

All GRAS 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 minimize the influence of stray capacitance and microphonic interference. The casing is made of stainless steel for maximum strength and durability. This preamplifier ensures reliable operation even under humid conditions owing to the heat generated by internal power dissipation.

The 26AC-1 is delivered with a built-in TEDS chip, and can be programmed as a single unit with a microphone fitted. An adaptor (GRAS GR0010) for GRAS 1/2" microphone cartridges is included.

Dynamic Range

GRAS 26AC-1 can handle both single and dual-sided power supplies. The supply can vary between 28 VDC and 120 VDC single-sided or ±14 VDC and ±60 VDC dual-sided. When using the high supply voltage (120 VDC or ±60 VDC), the dynamic range exceeds 140 dB. 

Noise

The electrical circuit in GRAS 26AC-1 is built on a ceramic substrate using selected low-noise components to gain very low self-noise. The electrical self-noise is so low that system noise is mainly determined by the microphone cartridge’s thermal noise.

Frequency response

The low-frequency cut-off of the GRAS 26AC-1 preamplifier is mainly determined by the input impedance of the preamplifier and the capacitance of the microphone cartridge (see the graph in the Specifications). The capacities 20 pF,6.5 pF and 3 pF equal the typical capacitances of 1/2", 1/4"" and 1/8" microphone cartridges respectively. The high-frequency cut-off is determined by the preamplifier’s ability to drive capacitive loads (slew rate), caused by the cable. For large-signals, the effects of these parameters must be accounted for when measurements are performed. A graph in the Specifications shows the large-signal response for GRAS 26AC-1 for various capacitive loads corresponding to different cable lengths. The output level is in decibels relative to 1 Volt. Typical capacitance for the cable is 100pF/m (30pF/foot).

Connector

The GRAS 26AC-1 1/4" Preamplifier is provided with a 5-pin LEMO series integrated connector. Cables for conversion to standard 7-pin LEMO series 1B plug are available.

 5-pin LEMO plug 00 male (ext. view)

 

Typical applications and use

General-purpose preamplifier

High-frequency measurements

High-pressure measurements

Specifications

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
-0.29
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
TEDS UTID (IEEE 1451.4)
27 v. 1.0
Connector type
5-pin LEMO 00
CE/RoHS compliant/WEEE registered
Yes / Yes, Yes
Weight
g / oz
6.9 / 0.24
Specification Conditions

Conditions: 23 °C Ambient temperature, ±60V/+120V power supply, 18 pF dummy microphone, 3 m output cable.

Typical frequency response for 1/2" (20 pF), 1/4" (6.5 pF) and 1/8" (3 pF) microphones

Typical max RMS output signal with 120 V and 30 V supply

GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.

Dimensions

Ordering info

Included items

GR0010

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

 

Optional items

GRAS AA0091

3 m LEMO 5-pin - LEMO 7-pin Cable

GRAS AA0092-CL

Customized Length LEMO 5-pin - LEMO 7-pin Cable

GRAS AL0029

1/4" Microphone Holder, POM

GRAS AL0013

1/4" Microphone Holder, Stainless Steel

GRAS AL0005

Swivel head

GRAS AL0006

Tripod

GRAS RA0063

Adapter for 1/8" microphone and 1/4" preamplifier

GRAS RA0006

Right-angled (90º) Adapter for 1/4" Microphone and 1/4" Preamplifier

GRAS RA0080

6pF Preamplifier-input adapter for 1/4" microphones

GRAS 12AA

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

GRAS 12AQ

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

GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.

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