Check the listing for details. Bruel & Kjaer (B&K) Type 2669-001 ½-INCH MICROPHONE PREAMPLIFIER, Tested. Condition: Used. Listed at 450.00 USD. This ½" microphone preamplifier operates over a wide range of temperature, humidity and other environmental conditions. USE SCENARIOSSound measurements with Brüel & Kjær 1/2" (1", 1/4" and 1/8" with adaptor) and compatible microphonesGeneral-purpose preamplifier and high-impedance input probe for Brüel & Kjær measuring instruments FEATURESThe preamplifier and its connectors all fulfill electromagnetic compatibility (EMC) requirementsCompact LEMO connector at preamplifier. Connector: lemo 0B 7 pinPatented charge-injection calibration technique for on-site calibration of the whole measuring channel including the microphoneWide dynamic rangeVery low inherent noise, high input impedanceLow output impedance and high output current allows use with long extension cablesWide working temperature range The 2669 has a very high input impedance presenting virtually no load to the microphone. The high output voltage together with an extremely low inherent noise level gives a wide dynamic range. The 2669's low output impedance allows the use of long extension cables without problems. You can connect ½" microphones directly and 1", ¼" and 1/8" types using adaptors. You can verify the condition of the microphone, preamplifier and cable on-site using its patented charge injection calibration technique. For more information please see Bruel & Kjaer website. Please note: Item and Item box holder is used and may show signs of use, tested and verified. Serial number may differ from pictured item. Item may not come with original box holder due to being unavailable. If you have any issues please let me know right away and I will make it right. Thank you for your business.