Lundahl LL1678 Amorphous Core Moving Coil Input Transformer

Highlights of the Lundahl LL1678

• Moving coil input transformer for MC pickup applications
• Amorphous strip core with mu-metal can
• Selectable turns ratios including 1:8, 1:16, and 1:32
• Excellent frequency response up to 90 kHz with balanced output
• Compact PCB-mount design measuring 30 x 22.5 x 14.5 mm
• All winding ends available on pins for flexible termination options

Product details Lundahl LL1678

Lundahl LL1678 Amorphous Core Moving Coil Input Transformer

The Lundahl LL1678 is designed for moving coil pickup input stages, making it a precise solution for MC cartridge front ends in turntables and high-quality home audio systems. Its winding structure uses two coils, each with one secondary winding surrounded by two primary windings, contributing to its wide and controlled frequency response.

The amorphous strip core is a key part of the LL1678 design. Unlike conventional mu-metal cores, this core material does not store energy, so low-frequency resonance with external series capacitors is practically eliminated. The transformer is housed in a mu-metal can and offers 3 kV isolation between windings and 1.5 kV isolation between windings and core.

All winding ends are brought out to the pins, allowing several termination alternatives and turns ratios. Recommended configurations include 1:8 for 150 ohm to 10 kΩ use, 1:16 for 25 ohm to 10 kΩ use, and 1:32 for 10 ohm to 10 kΩ use. This flexibility makes the LL1678 suitable for carefully tuned audio components and custom phono input designs.

Performance figures include a frequency response of 10 Hz to 90 kHz within ±1 dB with balanced output, or 10 Hz to 35 kHz within ±1 dB with unbalanced output, using termination alternative A. Distortion is below 0.5% at -8 dBU and 50 Hz with the primaries connected in series and a 50 ohm source impedance. The compact PCB footprint uses 2.54 mm pin spacing, 22.86 mm row spacing, a recommended 1.5 mm PCB hole diameter, and weighs 27 g.