Langevin 252-A (c. 1961)

The Langevin 252-A survives in the archive mostly as a pair of advertisements. No research notes or manual material were provided for this page. The confirmed record is almost entirely what Langevin itself printed in 1961.

Langevin's ad in Audio (August 1961, p.9) called it the "Model EQ-252-A Graphic Equalizer." It was pitched as a professional unit with seven switchable positions for variable high/low equalization and attenuation, aimed at recording, TV broadcast, and motion picture work. The same ad ran again in Audio (November 1961, p.9). Here is what Langevin claimed:

Circuit: bridged T
Impedance: 600/600 ohms
Insertion loss: 16 dB
Operating level: roughly -70 to +24 dBm
Positions: 7, with 8 dB of equalization

No independent review with measurements has surfaced in the material available to the archive, so those are the manufacturer's claims, not measured results. Beyond the two advertisements, nothing later in the archive mentions the EQ-252-A — a professional Langevin equalizer promoted through 1961 and otherwise undocumented.