Lundahl LL1935 Microphone Direct Input Transformer

Highlights of the Lundahl LL1935

• Designed for DI applications and 1:10 microphone input use
• Turns ratio of 1 + 1 : 5 + 5
• High permeability mu-metal core with mu-metal case shielding
• Electrostatic shield between primary and secondary windings
• Low capacitance winding technique for the high impedance windings
• Compact PCB-mount format, 38 x 23 x 16 mm and 46 g

Product details Lundahl LL1935

Lundahl LL1935 Microphone Direct Input Transformer

The Lundahl LL1935 is built for Direct Input applications where a high impedance source, such as a guitar pickup, needs to feed a low impedance microphone preamp input. As a precision audio component, it is also well suited to 1:10 microphone input applications, giving builders a flexible transformer for compact DI and microphone front-end designs.

Internally, the LL1935 uses two coils, each with one primary and one secondary winding separated by an electrostatic shield. The high impedance windings use a special low capacitance winding technique, while the high permeability mu-metal core and encapsulated mu-metal case provide effective magnetic shielding. For best performance, the high impedance side, marked 5 + 5, should be connected in series.

Performance is specified across a wide audio bandwidth. In 10:1 use with a 100 kΩ source and open secondary, the response is 20 Hz to 20 kHz at +0 / -3 dB. With a 1 kΩ load, the 10:1 response extends from 10 Hz to 45 kHz at +0 / -2 dB. In 1:10 operation with a 200 Ω source and open secondary, the response is 10 Hz to 80 kHz within ±1 dB, with no self-resonance detected in the stated configurations.

The transformer is designed for PCB mounting, with 5.08 mm pin spacing, 27.94 mm row spacing, a recommended PCB hole diameter of 1.5 mm, and a weight of 46 g. Static resistance is 650 Ω for each primary and 17 Ω for each secondary. For verification and electric measurements, the LL1935 also provides clear isolation ratings of 4 kV between windings and 2 kV between windings and shield.