LL1623AM 90mA Lundahl SE OPT Amorphous Ausgangsübertrager

Lundahl LL1623AM/90 amorphous-core SE output transformer

The Lundahl LL1623AM/90 is the amorphous high-end version of the configurable LL1623 single-ended output transformer. It supports primary loads of 1.6, 3.0 or 5.6 kΩ and is intended for a nominal primary current of 90 mA.

The amorphous core is aimed at amplifier projects that prioritise fine-signal behaviour and detail over maximum low-frequency power capability. Compared with the standard silicon-iron C-core, it provides less saturation headroom and lower power bandwidth.

Suitable applications

• Detail-oriented 300B, PX4 and PX25 single-ended amplifiers
• Amorphous-core EL34, KT88 and 6550 SE output stages
• High-end upgrades with sufficient low-frequency power reserve
• SET projects balancing idle current and magnetic headroom

Technical specifications

Transformer type

Open-frame single-ended valve-amplifier output transformer

Core material

Amorphous Lundahl audio C-core

Nominal primary current

90 mA; operation at a lower idle current is possible

Air gap

Approximately 190 µm in accordance with the standard LL1623/90mA construction

Primary inductance

30 H in accordance with the 90 mA base version

Primary load impedances

1.6 kΩ, 3.0 kΩ or 5.6 kΩ, including transformer copper resistance

Secondary load impedances

4 Ω, 8 Ω or 16 Ω, depending on the primary connection

Saturation flux

Approximately 33% lower for the amorphous core than for the corresponding silicon-iron core

Power bandwidth

Approximately 50% lower than the corresponding standard transformer according to Lundahl

Primary DC resistance

164 Ω with all primary sections connected in series

Primary leakage inductance

4.6 mH with all primary sections connected in series

Insulation

3 kV between primary and secondary windings and 1.5 kV between windings and core

Dimensions and weight

Approximately 118 × 85 × 78 mm at approximately 2.5 kg

Mounting

Four M4 mounting holes on an approximately 90 × 53 mm pattern; 5.08 mm pin spacing

Manufacturer and origin

Lundahl Transformers AB, made in Sweden

Available impedance combinations

5.6 kΩ primary

Configurable for 8 Ω or 16 Ω loudspeakers

3.0 kΩ primary

Configurable for 4 Ω, 8 Ω or 16 Ω loudspeakers

1.6 kΩ primary

Configurable for 4 Ω, 8 Ω or 16 Ω loudspeakers

Amorphous or standard C-core?

Amorphous version

Attractive for detail-oriented high-end projects when the required full-power bass capability remains safely within the available headroom

Standard version

Provides greater magnetic saturation reserve and is often the more robust choice for high output or deep full-power bandwidth

Interchangeability

The connection principle, impedances and physical size generally correspond to the standard LL1623/90mA, but the reduced power bandwidth must be considered

The open-frame transformer is intended for protected installation inside an amplifier chassis. Primary terminals and anode wiring may carry hazardous high voltage.

Questions about choosing an amorphous output transformer

Which amorphous high-end output transformer suits a 300B, PX4 or PX25 amplifier?

The Lundahl LL1623AM/90 is an attractive amorphous option for correctly designed 300B, PX4 and PX25 single-ended stages. A 3.0 or 5.6 kΩ primary may be selected according to the load line. Idle current and expected bass power must be chosen so that the lower saturation reserve of the amorphous core does not become the limiting factor.

Which amorphous output transformer suits an EL34, KT88 or 6550 single-ended amplifier?

The Lundahl LL1623AM/90 suits EL34, KT88 and 6550 SE stages when idle current does not exceed approximately 90 mA and the load line matches 1.6, 3.0 or 5.6 kΩ. It is particularly attractive for detail-oriented amplifiers using moderate full power, while the standard LL1623/90mA provides greater core headroom for maximum bass output.

Can I use the LL1623AM/90 instead of the standard LL1623/90mA?

Yes, when the primary impedance, idle current, secondary connection and physical dimensions are compatible. The general connections correspond to the standard LL1623 family. The amorphous core saturates approximately 33% earlier and Lundahl specifies about 50% lower power bandwidth, so low-frequency output capability must be reassessed before substitution.

Is the LL1623AM/90 suitable for a detail-focused high-end upgrade?

Yes, when fine-signal behaviour and subjective transparency take priority and the amplifier does not require maximum full power at the lowest bass frequencies. Lundahl reports a more transparent and subjectively wider-band character from amorphous versions, although the final result remains dependent on the valve, operating point, loudspeaker and complete circuit.