LL1620 60mA Lundahl SE OPT AÜ 3,3K 6,0k Übertrager transfor.

Lundahl LL1620/60mA – single-ended output transformer with 3.3, 6.0 or 11.5 kΩ

The Lundahl LL1620/60mA is a large single-ended output transformer for correctly designed valve output stages. The 60 mA version uses an air gap matched to this magnetic quiescent current and provides approximately 60 H of primary inductance.

Its divided primary and secondary windings support 3.3, 6.0 or 11.5 kΩ primary loads with several speaker impedances. The LL1620 uses Lundahl's audio C-core and a highly sectioned winding intended to reduce leakage inductance and winding capacitance.

Suitable applications

• Single-ended output stages operating at approximately 60 mA plate current
• Correctly designed 2A3, PX4, 45 and related power-triode stages
• 6V6GT and other pentodes or beam tetrodes in triode or pentode connection
• Primary loads of 3.3, 6.0 or 11.5 kΩ
• Mono and stereo high-end DIY projects using one transformer per channel
• 4, 8 or 16 Ω loudspeakers, depending on the primary connection

Technical data

Product type

Single-ended valve output transformer

Model version

LL1620/60mA

Rated magnetic operating point

60 mA DC at approximately 0.9 T

Air gap

Approx. 190 µm

Primary inductance

Approx. 60 H for the 60 mA version

Primary impedances

3.3, 6.0 or 11.5 kΩ plate load, depending on winding connection and loudspeaker load

Secondary impedances

4, 8 or 16 Ω at 3.3 and 6.0 kΩ; 8 or 16 Ω at 11.5 kΩ in the standard connections

Winding ratio

4 × 19.2:8 × 1

Primary DC resistance

Approx. 308 Ω with all sections in series, comprising four sections of approximately 77 Ω

Secondary DC resistance

Approx. 0.4 Ω per secondary section

Primary leakage inductance

Approx. 11 mH

Maximum primary signal voltage

Approx. 380 V RMS at 30 Hz in single-ended operation

Magnetic power limit at 11.5 kΩ

Approx. 13 W at 30 Hz; not a guaranteed amplifier-output rating

Magnetic power limit at 6.0 kΩ

Approx. 25 W at 30 Hz; not a guaranteed amplifier-output rating

Magnetic power limit at 3.3 kΩ

Approx. 50 W at 30 Hz; not a guaranteed amplifier-output rating

Winding loss

Approximately 0.2, 0.5 or 0.8 dB depending on the primary load

Thermal primary-current limit

150 mA according to the 7 W loss criterion; not a recommended single-ended bias current

Winding-to-winding dielectric test

3 kV AC

Winding-to-core dielectric test

1.5 kV AC

Core

Lundahl audio C-core

Construction

Open-frame construction with solder terminals

Dimensions

Approx. 118 × 85 × 78 mm

Mounting pattern

Approx. 53 × 90 mm with four M4 mounting points

Weight

Approx. 2.5 kg

Choosing the primary load

3.3 kΩ plate load

Tends towards greater current and potentially more output; plate and, where applicable, screen-grid dissipation require careful verification

6.0 kΩ plate load

Intermediate load option for many triodes and triode-connected output valves

11.5 kΩ plate load

Higher load with lower current and greater required voltage swing; standard connections support 8 or 16 Ω speakers

Comparison of current versions

LL1620/40mA

125 µm air gap and approximately 90 H primary inductance; more inductance and bass reserve at lower quiescent currents

LL1620/60mA

190 µm air gap and approximately 60 H; intermediate single-ended current version

LL1620/80mA

250 µm air gap and approximately 45 H; intended for greater magnetic quiescent current but with lower primary inductance

Installation and safety notes

The 60 mA suffix describes the magnetic design point rather than the maximum thermal winding current. The plate current, signal current, primary load and maximum core flux must be considered together.

Operation below 60 mA is possible. At a substantially lower current, however, the 40 mA version can offer greater bass reserve because of its higher primary inductance.

Connect the secondary sections exactly as shown in the Lundahl diagram. Not every primary load supports the same 4, 8 and 16 Ω alternatives.

Lethal plate voltages may be present on the open transformer. Install it inside a closed, touch-safe enclosure with adequate insulation clearances, strain relief and mechanical support for its weight.

Questions about selection and use

Which single-ended output transformer suits a 2A3, PX4, 45 or 6V6 stage operating at approximately 60 mA?

Lundahl LL1620/60mA is designed around a magnetic operating point of approximately 60 mA and provides 3.3, 6.0 or 11.5 kΩ plate loads. The exact value must be selected from the valve type, plate voltage, quiescent current and required load line.

Which Lundahl single-ended output transformer provides 3.3, 6.0 and 11.5 kΩ together with several speaker impedances?

Lundahl LL1620/60mA provides these three primary loads. Standard connections provide 4, 8 and 16 Ω at 3.3 and 6.0 kΩ, while 8 and 16 Ω are provided at 11.5 kΩ.

Can the 60 mA version also operate at a lower quiescent current?

Yes, the LL1620/60mA can operate at a lower quiescent current when the load line and signal swing are suitable. At substantially lower current, the 40 mA version can provide greater bass reserve because of its higher primary inductance.

Is the Lundahl LL1620/60mA suitable for a correctly designed 6V6GT single-ended amplifier?

Yes, the Lundahl LL1620/60mA can be used in a correctly designed 6V6GT single-ended amplifier. The primary load, plate and screen-grid voltages, quiescent current, operating mode and expected output must be verified together.