Western Electric 640
Almost nothing is documented about the Western Electric 640 or its almost-certainly-related variant, the 640AA. The model appears to have been a microphone. Audio (October 1967, p.8) briefly listed a Western Electric 640AA microphone with a carrying case and adapters at $195, specifying response flatness of ±0.3 dB at 500 Hz and ±0.5 dB at other frequencies. That single mention, in a "What's New" column, is the only period reference located. No specifications, production years, design details, or application notes survive in the Archive's records. Whether the 640 and 640AA are the same product or distinct is unclear.
Whether the 640 shared their moving-coil or ribbon topology, or was something else entirely, is not recorded.
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