Hammond 813A 150 Ohm Mic or Line to Base Audio Transformer

The 813A is a broadcast-quality 800A Series audio transformer for feeding a line signal or a 150 ohm microphone into a transistor base input. It pairs a nominal 125/500 ohm primary (150/600 ohms also listed) with a 600/2400 ohm secondary (720/2880 ohms also listed).

Maximum primary D.C. unbalanced current is 0.4 mA. Frequency response is +/- 0.5 dB max. from 50 Hz to 15 kHz, insertion loss is approximately 1 dB, and the maximum power level is +15 dBm with the specified characteristics, or higher with reduced low frequency performance. The series notes that operating below nominal impedance lowers power capability and shifts the frequency spectrum downward, while higher impedances shift both upward.

Humbucking construction helps reject stray magnetic fields, and balanced split windings on both primary and secondary give circuit versatility; the primary may be used as the secondary and vice versa for impedance matching. An electrostatic shield sits between the primary and secondary windings.

It is housed in a deep-drawn steel case with a tin plated finish and fastens with two 6-32 mounting studs, supplied with hardware. Connections are made by wire leads of at least 4" in length. Maximum overall dimensions are 1.75" (44.5 mm) wide x 1.25" (31.8 mm) deep x 2.56" (65 mm) high. The 813A is RoHS and REACH compliant. Its listed shipping weight is 0.55 lbs (0.25 kg), and it is identified by UNSPSC 39121301.