Hammond 124E 15K CT to 33.8K/135K Dual-Secondary Interstage

The 124E is a 5 watt tube driver interstage transformer with a 15K ohm centre-tapped primary and a dual secondary winding. It is built for general purpose or replacement use in push-pull or phase inverter tube driver circuits, and suits amplifier builders who want one part that can present two secondary impedances.

The two secondary windings can be connected in parallel for a 33.8K ohm secondary or in series for a 135K ohm secondary:

• Parallel (33.8K ohm): connect the GRN/YEL wire to the GRN wire and the BLK/YEL wire to the BLK wire.
• Series (135K ohm): connect the BLK/YEL wire to the GRN wire, which becomes the centre tap; the GRN/YEL and BLK wires are the output.

DC resistance is 728 ohms on the primary and 3880 ohms on the secondary. The core uses grain-oriented steel laminations, and the series is specified for a minimum frequency response of 150 Hz to 15 kHz (+1/-3 dB) referenced to 1 kHz.

The 124E is an open style transformer with primary leads a minimum of 5 inches long. Outline dimensions are A 2.88 in (73 mm), B 1.74 in (44 mm), C 2.37 in (60 mm) and D 2.38 in (60 mm), with 0.19 in (5 mm) mounting holes. Shipping weight is 1 lb (0.45 kg).

Like the rest of the 124 Series it has no gap for DC bias current, so it should not be used in single ended applications. It is RoHS and REACH compliant.