124A

Overview

The Hammond Manufacturing 124A is an audio interstage transformer designed for tube driver applications in push-pull circuits. It features a primary impedance of 10 kOhms and a secondary impedance of 90 kOhms with a 1:3 turns ratio. The unit supports a power rating of 5 watts and operates within a frequency range of 150 Hz to 15 kHz. Electrical characteristics include a primary DC resistance of 403 Ohms and a secondary DC resistance of 1.524 Ohms. The component utilizes SMD/SMT termination and measures 1.43 inches in length, 1.35 inches in width, and 2.38 inches in height.

Feature Summary

• Designed specifically for tube driver and interstage coupling in push-pull amplifier configurations
• Utilizes grain-oriented steel construction for signal transformation
• Provides electrical isolation between circuit stages without shielding

Applications

• Tube driver interstage coupling
• Push-pull output circuit replacement
• General-purpose audio signal transformation

Procurement Notes

Verify the specific termination style required for the target PCB or chassis mount application, as specifications indicate SMD/SMT compatibility but physical implementation may vary. Confirm that the 10k/90k impedance ratio aligns with the vacuum tube plate and grid requirements of the intended circuit design before finalizing the order.

Selection Notes

Select this component when a 1:3 step-up ratio is required for driving subsequent tube stages from a previous driver. Ensure the 5-watt power handling capacity meets the peak signal demands of the audio system. Consider the unshielded nature of the unit regarding electromagnetic interference sensitivity in dense circuit layouts.

Part Context

This part belongs to the Hammond 124 Series of audio transformers. It is categorized under Tube Application Power Transformers and Audio & Signal Transformers. The series is known for providing reliable interstage coupling solutions for vintage and modern tube-based audio equipment designs.

Replacement Considerations

The Hammond 124C is a documented substitute within the same series, offering identical 10k/90kCT impedance specifications and 5W power rating. Verify mounting style differences, as the 124C is explicitly noted for chassis mounting with wire leads, whereas the 124A specifies SMD/SMT termination.