Lundahl LL1680-5 Output Transformer for Tube Amplifiers 5mA

Highlights of the Lundahl LL1680-5

• Line output transformer for tube amplifier applications
• 5 mA primary DC current for 0.9 Tesla operation
• Configurable for 15k:600 ohm or 15k:150 ohm balanced and unbalanced outputs
• 210 H primary inductance with frequency response down to 15 Hz
• Paper insulation in the high-impedance sections to minimize internal capacitance
• Special Lundahl audio C-core construction

Product details Lundahl LL1680-5

Lundahl LL1680-5 Line Output Transformer for Tube Amplifiers 5mA

The Lundahl LL1680-5 is made for line output use in tube amplifiers and is designed to match or exceed the specifications of the UTC LS-27 transformer. Its 9 + 9 : 1 + 1 + 1 + 1 winding structure allows multiple connection alternatives, giving builders practical flexibility for different output requirements.

For balanced 15k:600 ohm operation, the transformer uses an 18:4 turns ratio and delivers a 15 Hz to 50 kHz frequency response at 15 kΩ source impedance and 600 Ω load. For unbalanced 15k:600 ohm operation, response is 15 Hz to 40 kHz. When configured for 15k:150 ohm operation, the balanced connection reaches 15 Hz to 55 kHz, while the unbalanced connection is specified at 15 Hz to 40 kHz.

The LL1680-5 uses paper insulation in the high-impedance sections instead of polypropylene foil to help reduce internal capacitance. Each coil consists of three sections to optimize leakage inductance against inter-winding capacitance, while the special audio C-core supports the transformer’s use in demanding audio components.

Key electrical ratings include 210 H primary inductance, 150 V RMS maximum primary signal voltage at 30 Hz, and isolation of 4 kV between primary and secondary windings and 2 kV between windings and core. The unit weighs 0.35 kg and is built with 4 x M3 mounting holes for secure installation.