Lundahl LL1684 Amorphous Core General Purpose Transformer

Highlights of the Lundahl LL1684

• High-level amorphous core transformer with 1 + 1 : 1 + 1 turns ratio
• Suitable for microphone input, line input, line output and galvanic isolation
• Symmetrical winding arrangement for phase-splitting input applications
• Two-coil structure improves immunity to external magnetic fields
• Primary and secondary windings separated by electrostatic shields
• Housed in a mu-metal can for additional magnetic shielding

Product details Lundahl LL1684

Lundahl LL1684 High-Level Amorphous Core General Purpose Transformer

The Lundahl LL1684 is designed as a versatile high-level transformer for professional audio signal paths. It can be used in audio components for microphone or line input, line output and galvanic isolation, making it a practical choice for balanced signal interfacing and isolation tasks.

Its 1 + 1 : 1 + 1 winding structure allows multiple connection options, including parallel-parallel 1:1 operation for low-loss isolation and serial-serial 1:1 operation for high-level line isolation. The winding arrangement also provides excellent symmetry when the transformer is used for phase splitting in 1 : 1 + 1 input configurations.

The two-coil construction improves immunity to external magnetic fields from nearby power supplies and motors. Primary and secondary windings are separated by electrostatic shields, and the complete transformer is housed in a mu-metal can, supporting clean integration in sensitive signal circuits and electromechanics projects.

Key electrical specifications include 41 ohm static resistance per primary and secondary winding, a self-resonance point above 250 kHz, and a 10 Hz to 100 kHz frequency response within ±1.0 dB with a 150 ohm source and 10 kΩ load in serial connection. The transformer measures 42 x 28 x 22 mm above the PCB, weighs 81 g, uses 5.08 mm pin spacing and has a recommended PCB hole diameter of 1.5 mm.