Western Electric 640 AA Microphone Capsule 1940's-1950's

Western Electric 640AA Laboratory / Calibration Microphone Capsule — Extremely Rare

Extremely rare original Western Electric 640AA condenser microphone capsule. This is the legendary laboratory-standard microphone developed by Western Electric/Bell Laboratories for precision acoustic measurement and calibration.

The 640AA was the improved version of the earlier 640A, incorporating a more stable steel diaphragm designed to minimize the effects of temperature, humidity and atmospheric conditions. It became an important reference microphone for precision acoustic measurement during the era.

The 640AA is particularly associated with the Western Electric RA-1095 amplifier, which was designed to operate with the 640AA. Together, the 640AA and RA-1095 formed a highly accurate laboratory measurement microphone system used for testing sound pickup and reproducing equipment.

The 640AA was also used as a precision calibration/reference microphone in laboratory work, including work associated with Bell Laboratories and the National Bureau of Standards (NBS). Historical technical documentation also shows 640AA microphones being used as reference standards in calibration work involving other microphone and audio equipment, including Altec equipment.

This was not simply a vintage studio microphone capsule. The 640AA was a precision laboratory measurement transducer and reference standard from the Western Electric/Bell Labs era, making it an important piece of early microphone and acoustic-measurement history.

Original 640AA capsules are exceptionally difficult to find today, particularly as loose original components. This is a very unusual opportunity for a serious Western Electric, Bell Labs, vintage microphone, recording-history or acoustic-measurement collection.

Important

This listing is for the original Western Electric 640AA capsule only, as pictured. The RA-1095 amplifier is not included.

Please examine all photographs carefully and ask any questions before purchasing.

A genuine piece of Western Electric / Bell Laboratories history and one of the rarest early laboratory condenser microphone components you are likely to encounter.

Tested and working. Comes with original metal capsule cover. see pics

Sold As Is.