2670 1/4-inch Microphone Preamplifier, integral 2m cable with 7-pin LEMO plug

The housing of Falcon Range 1/4-inch Microphone Preamplifier Type 2670 is made completely out of stainless steel and is supplied with a 2 m fixed cable terminated with a LEMO connector for input at the instrument end. The preamplifier is very compact and operates over a wide range of temperature, humidity and other environmental conditions. It has a very high input impedance presenting virtually no load to the microphone. The high distortion limit together with an extremely low inherent noise level gives a wide dynamic range.1/4-inch Microphone Preamplifier Type 2670 is a Falcon Range product for precision acoustic measurements with Brüel & Kjær’s wide range of condenser microphones. You can connect 1/4-inch microphones directly and 1/8-inch types using an adaptor. The preamplifier, cable and its connectors all fulfil EMC requirements.You can verify the condition of the microphone, preamplifier and cable on-site using its patented charge injection calibration (CIC) technique. The preamplifier’s low output impedance allows the use of long extension cables without problems.

Product Data

Uses

Sound measurements with 1/4- and 1/8-inch Brüel & Kjær and other compatible microphones
Sound intensity probes

Features

Full electromagnetic compatibility (EMC)
LEMO connector for instrument input socket
Patented charge injection calibration technique for on-site calibration of the whole measuring channel including the microphone
Wide dynamic range
Very low inherent noise, high input impedance
Low output impedance and high output current allow use with long extension cables
Wide working temperature range
Excellent phase linearity

The low output impedance and high output current capability mean that you can use long cables between the preamplifier and your measuring instrument without loss of signal quality. The preamplifier is supplied in an elegant yet strong plastic box made from recyclable materials.

EMC Certification

The preamplifier complies with EMC (electromagnetic compatibility) requirements specified in EN 50082 – 1 (residential, commercial and light industry) as well as in EN 50082 – 2 (industrial environment). These are generic European standards for noise immunity, to ensure that electrical instruments are not disturbed by other electrical appliances. To get the full benefit of this certification, the preamplifier must be connected to an instrument which also complies with EMC requirements.

Charge Injection Calibration

This is a patented technique for verifying the entire measurement setup including the microphone, preamplifier and connecting cable.

Brüel & Kjær’s Patented Charge Injection Calibration Technique

The charge injection calibration technique is a method for remotely verifying the condition of the entire measurement setupincluding the microphone. This is a great improvement over the traditional insert-voltage calibration method which virtually ignores the state of the microphone. The CIC technique is very sensitive to any change in the microphone’s capacitance, which is a reliable indicator of the microphone’s condition.

The technique works by introducing a small but accurately defined capacitance C c (typically 0.2 pF) with a very high leakage resistance (greater than 50 000 GW) into the circuit of the preamplifier, see illustration below (upper diagram). C i and R i represent the preamplifier’s high input impedance and A its gain (ª 1).

For a given calibration signalV i, the output V o of this arrangement will change measurably, even for small changes in the microphone’s capacitanceC m. The...

For a full Description and Specifications, see Product Data