LL1620 Output Transformer

The Lundahl LL1620 is a C-core output transformer designed for tube amplifiers. Depending on how the windings are connected, the primary can be configured for 3.3K, 6K, or 11.5K ohms, while the secondary can provide 4, 8, or 16 ohms. Buyers can also choose between different circuit configurations and core materials when ordering.

The transformer uses multiple carefully proportioned winding sections to keep leakage inductance extremely low. Combined with a winding method that reduces capacitance, this design delivers an exceptionally wide frequency response. The core is a custom audio-grade C-core produced by Lundahl, factory-gapped to match the DC current of the output tubes. The unit has an open-frame construction and is intended for mounting inside an amplifier chassis.

The LL1620 is offered in four versions, each with a factory-set air-gap:

• Push-pull

• Single-ended 40 mA

• Single-ended 60 mA

• Single-ended 80 mA

(The air gap allows the core to carry the tubes’ DC current without saturating, while still providing headroom for the audio signal.)

Two core material options are available:

• Silicon-iron

• Amorphous-iron (AM)

By wiring the transformer’s exposed solder pins in different ways, the builder can achieve the following primary/secondary impedance combinations:

Primary – Secondary
• 11.5K → 8 or 16 Ω
• 6K → 4, 8, or 16 Ω
• 3.3K → 4, 8, or 16 Ω

Overall dimensions (including pins): 118 × 85 × 78 mm

Made to order – typical lead time 4 weeks.