Hammond 124C Coil-Only Interstage Winding, 10K to 90K CT

The 124C is the coil only version of the 124 Series tube driver interstage transformer. It is the same coil used in the 124A and 124B, sold without laminations for experimenters who want to use their own iron, alloy or specialty core. It suits tube audio builders who want control over core material in a push-pull or phase inverter driver stage.

Electrically the winding is rated 5 watts, with a 10,000 ohm primary and a 90,000 ohm centre-tapped secondary, a 1:3 turns ratio and 500 Vrms dielectric strength. Typical DC resistance is 405 ohms on the primary and 1525 ohms on the secondary (the ordering table lists 403 and 1524 ohms).

Because it is supplied without a core, the drawing gives inductance measured with no core at 1.0 kHz, 1.0 V OC: 0.13 H on the primary and 0.914 H on the secondary. Impedance at the same conditions is 0.57 kOhm primary and 5.52 kOhm secondary. Final performance will depend on the core you assemble it with.

Leads are a minimum of 5 inches long. Primary leads are RED and BLUE; the secondary is GREEN - BLACK - GREEN with black as the centre tap. The coil label reads 5W 150Hz - 15kHz. There are no outline dimensions for the 124C because no laminations or mounting hardware are included. Shipping weight is 1.2 lbs (0.54 kg), and the part is RoHS and REACH compliant.