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 influenceof 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.
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 exceeding126 dB.
The electrical circuit in Type 26CG preamplifier isbuilt 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 (Type 40AZ’s) thermal noise.
The low-frequency cut-off of the Type 26CG preamplifier is mainly determined by the input impedance of the preamplifier and the capacitance of the microphone capsule. The capacities 20 pF,6.5 pF and 3 pF equal the typical capacitances of ½″, ¼″ and ⅛″ microphone capsules 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.
Type 26CG is typically used with Type 40AZ, low frequency microphone capsule to reach a -3-dB cut-off frequency around 0.25 Hz.Connectors and Adapter Preamplifier Type 26CG is provided with a 3-m lightweight cable terminating in a BNC plug. The amplifier is connected to the cable via a Microdot connector. The cable is only 2.0 mm in diameter and withstands temperatures from - 40 oC to +150 oC. An adaptor (GR0010) for G.R.A.S. ½″ microphones is included.
*) Constant Current Power, equal to IEPE
**) Transducer Electronic Data Sheet - as specifi ed byIEEE-1451.4
|Frequency response (±0.2 dB) with 18 pF microphone dummy and 4.7 nF cable load||Hz||1 to 200 k|
|Input impedance||GΩ // pF||TBD|
|Output Voltage Swing, max. @ 24 V bias voltage||Vp||8|
|Noise (A-Weighted) maximum||µV||2.5|
|Noise (A-Weighted) typical||µV||1.8|
|Noise (Linear 20 Hz – 20 kHz) maximum||µV||6|
|Noise (Linear 20 Hz – 20 kHz) typical||µV||3.5|
|Power supply (Constant Current Power)||mA||2 to 20 (typ. 4)|
|DC-offset, minimum, single suppy||V||TBD|
|DC-offset, maximum, single suppy||V||TBD|
|DC-offset, balanced supply||V||TBD|
|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||Microdot 10/32|
|CE/RoHS compliant/WEEE registered||Yes / Yes, Yes|
|Weight||g / oz||6.00 / 0.21|
|Weight with cable and connector||g / oz||TBD / TBD|
|G.R.A.S. GR0010||¼" to ½" adapter for use with G.R.A.S. ½! microphones|
|G.R.A.S. AA0018||Extension cable, Microdot(UNF 10-32) to BNC, 3 metres|
|G.R.A.S. RA0001||Right-angled (90º) Adapter for½" microphone and ¼" preamplifier|
|G.R.A.S. RA0003||Adapter for ½" microphone and¼" preamplifier|
|G.R.A.S. RA0006||Angled (90º) Adapter ¼! to ¼"|
|G.R.A.S. AA0060||Extension cable, Microdot(UNF 10-32) to BNC,1 meter|
|G.R.A.S. AA0061||Extension cable, Microdot(UNF 10-32) to BNC, 5 metres|
|G.R.A.S. AA0062||Extension cable, Microdot(UNF 10-32) to BNC, 10 metres|
|G.R.A.S. AE1038||Microdot (UNF 10-32) Adapter(Female-Female)|
|G.R.A.S. AA0013||Tripod adapter for ¼" preamplifier|
|G.R.A.S. RA0096||Tripod adapter for ¼" preamplifier with angular adjustment|