GRAS 26AS 1/4" Standard Preamplifier with 3 m Integrated Cable, Very Short
Freq range: 2.5 Hz to 200 kHz
Noise: 6 µV Gain: -0.29 dB
Special feature: Very short
The GRAS ¼" Preamplifier Type 26AS is a small robust unit short enough for use in confined spaces, e.g., for binaural measurements with the KEMAR Manikin (GRAS 45BB or GRAS 45BC) or GRAS 45CA Hearing-protector Test Fixture. It has a very low inherent-noise level, a wide dynamic range, and a frequency response from below 2 Hz to above 200 kHz.
Technology
Typical applications and use
- Confined spaces
- High frequency measurements
- High pressure measurements
- Sound intensity measurements
- Near-field measurements
- Anechoic boxes
- Hearing-aid measurements
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 ensures reliable operation under humid conditions owing to the heat generated by internal power dissipation.
Dynamic Range
GRAS 26AS 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 VDCor ±60 VDC), the dynamic range exceeds140 dB.
Noise
The electrical circuit in GRAS 26AS 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 capsule’s thermal noise.
Frequency response
The low-frequency cut-off of the GRAS 26AS preamplifier is mainly determined by the input impedance of the preamplifier and the capacitance of the microphone capsule. The capacities 20 pF,6.4 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 (slewrate), caused by the cable. For large-signals, the effects of these parameters must be accounted for when measurements are performed. The large-signal response for Type 26AS for various capacitive loads corresponding to different cable lengths is shown in the data sheet. The output level is in decibels relative to 1 Volt. Typical capacitance for the cable is 100 pF/m(30pF/foot).
Connector
The GRAS 26AS is provided with a 3 m lightweight cable terminating in a 7-pin LEMO series 1B plug. The cable is only 2.5 mm in diameter and will withstand temperatures from–40 °C to +150 °C. An adaptor GR0010 for GRAS 1/2" microphones is included.
7-pin LEMO plug 1B male (ext. view)
Specifications
Conditions: 23 °C Ambient temperature, ±60V/+120V power supply, 18 pF dummy microphone, 3 m output 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
Adapter for 1/4" preamplifier and 1/2" microphone |
Optional items
1/4" Microphone Holder, POM |
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1/4" Microphone Holder, Stainless Steel |
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Swivel head |
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Tripod |
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GRAS RA0063 |
Adapter for 1/8" microphone and 1/4" preamplifier |
Right-angled (90º) Adapter for 1/4" Microphone and 1/4" Preamplifier |
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6pF Preamplifier-input adapter for 1/4" microphones |
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2-Channel Power Module with gain, filters and SysCheck generator |
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2-Channel Universal Power Module with signal conditioning and PC interface |
GRAS Sound & Vibration reserves the right to change specifications and accessories without notice.