Lundahl LL1539 Line Output Transformer for Tube Amplifiers

Highlights of the Lundahl LL1539

• Audio output transformer for balanced drive
• Turns ratio of 2 : 1 + 1
• Frequency response of 20 Hz to 60 kHz, ±0.3 dB
• Maximum output level of +24 dBU at 20 Hz with 600 Ω load
• Primary to secondary isolation of 4 kV
• Compact PCB-mounted design with 47 x 34 x 21 mm dimensions

Product details Lundahl LL1539

Lundahl LL1539 Audio Output Transformer for Balanced Drive

The Lundahl LL1539 is a precision audio output transformer for balanced drive, making it a focused choice among discrete audio components for line-output stages in tube amplifiers. Its winding arrangement places the secondary windings between neutral sections of the primary windings when connected correctly, reducing the effect of capacitance between primary and secondary.

With a 2 : 1 + 1 turns ratio, the LL1539 is built for balanced output applications where signal integrity and output symmetry matter. The transformer delivers an output balance greater than 65 dB under IRT conditions with a source below 10 Ω and a 600 Ω load.

Performance is strong across the audio band and beyond, with a frequency response of 20 Hz to 60 kHz at ±0.3 dB, measured at 10 dBU with a source below 10 Ω and a 600 Ω load. Maximum output level before saturation is +24 dBU at 20 Hz with a 600 Ω load, while midband voltage loss across the transformer is 1 dB.

The LL1539 is designed for PCB mounting with 5.08 mm pin spacing, 35.56 mm row spacing and a recommended PCB hole diameter of 1.5 mm. It measures 47 x 34 x 21 mm above the PCB and weighs 130 g. Isolation is rated at 4 kV between primary and secondary windings and 2 kV between windings and core.