GRAS 26CG 1/4" CCP Preamplifier with Microdot Connector, Low Frequency

Freq range: 1 Hz - 200 kHz
Noise: 1.8 µV Gain: -0.35 dB
Special feature: For low-frequency applications

Technology

Typical Applications

  • Infra-sound measurements
  • Low-level measurements
  • General-purpose preamplifier
  • Use with 40AZ ½″ Free-field Microphone, Low-frequency

Special Properties

  • Wide Frequency Range
  • Low Cut-off Frequency
  • Low Noise Level

GRAS 26CG can easily be connected to any IEPE input or to a GRAS 12AQ or 12AL Power Supply.

The 26CG is delivered with a built-in TEDS chip and can be programmed as a combined unit with a microphone fitted. It can be used with all GRAS prepolarized microphones.

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 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 this preamplifier ensure reliable operation under humid conditions owing to the heat generated by internal power dissipation.

Dynamic Range

The lower limit of the dynamic range is determined by the noise floor. The upper limit of the dymamic range is determined by the power module: Type 12AQ, sourced at 28 V DC, supplies a constant current of 4 mA. This leads to a maximum output voltage of 8 Vpeak, the dynamic range thereby exceeding 126 dB.

Noise

The electrical circuit in the GRAS 26CG preamplifier 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 (GRAS 40AZ’s) thermal noise.

Frequency Response

The low-frequency cut-off of the 26CG preamplifier is mainly determined by the input impedance of the preamplifier and the capacitance of the microphone cartridge. The capacities 20 pF,6.5 pF and 3 pF equal the typical capacitances of ½″, ¼″ and ⅛″ microphone cartridges respectively.

The high-frequency cut-off is determined by the preamplifier’s ability to drive capacitive loads (slewrate), caused by the cable. For large-signals, the effects of these parameters must be accounted for when measurements are performed.

GRAS 26CG is typically used with GRAS 40AZ, low frequency microphone cartridge to reach a -3-dB cut-off frequency around 0.25 Hz.

Connectors and Adapters

26CG Preamplifier is provided with a Microdot connector. An adaptor (GR0010) for GRAS 1/2" microphones is included.

Specifications

Frequency range (±0.2 dB) with 18 pF microphone dummy
Hz
1 to 200 k
Slew rate
V/µs
20
Input impedance
GΩ // pF
40 // 0.4
Output impedance
Ω
< 50
Output Voltage Swing, min. @ 24-28 V CCP voltage supply
Vp
8
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
-0.35
Power supply (Constant Current Power)
mA
2 to 20 (typ. 4)
DC bias voltage, typ.
V
12
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)
769 v. 0.9
Connector type
Microdot 10/32
CE/RoHS compliant/WEEE registered
Yes / Yes, Yes
Weight
g / oz
6.0 / 0.21
Specification Conditions

Conditions: 23 °C Ambient temperature, 4 mA / 24 V open loop CCP voltage, 18 pF dummy microphone & 3 m coax-cable.

 

Typical low-frequency response of Type 26AL for ½″ (20 pF), ¼″ (6.5 pF) and ⅛″ (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 AA0070

3 m Microdot - BNC Cable

GRAS AA0073-CL

Customized Length Microdot - BNC Cable

GRAS AA0087-CL

Customized Length Microdot - Microdot 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 12AL

1-Channel CCP Power Module with A-weighting filter

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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