LL1681 Lundahl MC-Übertrager Moving Coil Input transformer

Lundahl LL1681 mu-metal MC transformer with Faraday shields

The Lundahl LL1681 is a moving-coil step-up transformer combining a large mu-metal core, two turns ratios and internal electrostatic shields. It provides a low-noise phono DIY option between the compact entry-level models and the Cardas-wound premium range.

Its 1:13 and 1:26 ratios suit cartridges including the Denon DL-103R, Audio-Technica AT33PTG/2, Rega Ania Pro, Ortofon Cadenza and low-output SPU variants.

Suitable applications

• Denon DL-103R, AT33PTG/2 and Rega Ania Pro
• Ortofon SPU Classic as a value-focused 1:26 solution
• Ortofon Cadenza and other low-impedance MC cartridges
• Low-noise phono designs requiring electrostatic shielding

Technical specifications

Transformer type

Passive moving-coil step-up transformer, one channel per component

Core material

Large mu-metal core

Winding construction

Two coils with sectioned primaries and a paper-insulated secondary winding

Electrostatic shielding

Internal Faraday shields between the primary and secondary windings

Step-up ratios

1:13 or 1:26

Voltage gain

Approximately 22.3 dB at 1:13 or 28.3 dB at 1:26

Cartridge load with a 47 kΩ MM input

Approximately 278 Ω at 1:13 or 70 Ω at 1:26 without additional loading

Documented frequency response

Approximately 7 Hz to 60 kHz within ±1 dB with balanced signal paths; approximately 7 Hz to 55 kHz in the documented unbalanced 1:13 arrangement

Insulation

4 kV between windings and 2 kV between the windings and core

Dimensions

Approximately 48 × 29 × 20 mm

Weight

Approximately 90 g

Stereo requirement

Two LL1681 transformers are required for stereo

Ratio and shielding notes

A 1:13 ratio is often the more universal starting point for cartridges producing approximately 0.25 to 0.5 mV. A 1:26 connection provides significantly more gain for very quiet cartridges, but a 47 kΩ MM input then reflects only about 70 Ω.

The Faraday shields help reduce capacitive interference but do not replace correct grounding. The step-up transformer should be positioned away from mains transformers, switch-mode supplies, motors and AC wiring.

Questions about choosing a shielded MC transformer

Which Lundahl transformer suits a Denon DL-103R or AT33PTG/2?

The LL1681 at 1:13 is an attractive starting point for both cartridges. The DL-103R produces approximately 3.25 mV and the AT33PTG/2 about 3.9 mV. The reflected load of roughly 278 Ω is relatively gentle. A 1:26 connection provides more output but loads the cartridge more heavily at approximately 70 Ω.

Which value-focused step-up transformer suits an Ortofon SPU Classic?

The LL1681 can be used at 1:26 as an economical alternative. A 0.2 mV cartridge output becomes approximately 5.2 mV and the reflected load from a 47 kΩ MM input is about 70 Ω. The LL1941 additionally provides 1:32 and a more elaborate amorphous Cardas premium construction.

Can the LL1681 Faraday shields reduce hum and interference?

Yes, the internal electrostatic shields can reduce capacitive interference between input and output. They must be grounded correctly according to the data sheet. Distance, orientation and a suitable metal enclosure remain important against strong magnetic fields.

Is the LL1681 an affordable alternative to the LL1941?

Yes, particularly when 1:26 provides sufficient gain and the reflected load suits the cartridge. The LL1681 uses a mu-metal core, standard copper and Faraday shields. The LL1941 provides 1:16 and 1:32, an amorphous core, Cardas OFC and premium dual-coil construction.