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General Radio 1232-A
Tuned amplifier and null detector
General Radio 1232-A Tuned Amplifier and Null Detector

Available from 1961 to 1978+

Catalog History
 Document Year Page
Catalog Q 1961 60
Catalog R 1963 79
Catalog S 1965 104
Catalog T 1968 115
Catalog U 1970 134
Catalog73 1973 162
Catalog78 1978 48
(All manuals in PDF format unless noted otherwise)

The General Radio 1232-A Tuned Amplifier and Null Detector was introduced in Catalog Q (1961) and remained available through Catalog 1978.

The 1232-A is a solid-state, battery-operated tuned amplifier and null detector. Its tuned frequency range covers 20 to 20 kHz in 5 bands, plus a flat response setting.

As a null detector, the 1232-A is part of the GR 1240-A Bridge Oscillator-Detector, the 1660-A Inductance Measurement System, and the 1620-A Capacitance Measurement System. Battery operation is provided by nine M72 cells (now obsolete).

The instrument shown in the photos below has been converted to a rechargeable battery pack. (Instructions for this conversion are covered in a document below.)


  • Frequency Response:
  • Tunable Filters: 20 Hz to 20 kHz in 3 ranges; 5% bandwidth; 2nd harmonic at least 34 dB down from peak, 3rd at least 40 dB down
  • 50 kHz and 100 kHz Filters: 2nd harmonic 44 and 53 dB down, respectively
  • Flat Response: ±3 dB from 20 Hz to 100 kHz
  • Input Impedance: Approximately 50 kΩ at maximum gain, varies inversely with gain to 1 MΩ at minimum gain
  • Gain: 120 dB on the tunable ranges; 100 dB, flat range; 106 dB at 50 kHz; 100 dB at l00 kHz position