LL1623 60mA Lundahl SE OPT AÜ 3,0k 5,6k Übertrager transfor.

Lundahl LL1623/60mA SE output transformer for 2A3 and EL84

The Lundahl LL1623/60mA is a configurable single-ended output transformer for classic power triodes and smaller audio output pentodes. Its audio C-core is gapped for 60 mA of primary DC current and supports primary loads of 1.6, 3.0 or 5.6 kΩ.

The combination of 46 H primary inductance, low leakage inductance and multiple secondary arrangements makes it particularly attractive for 2A3, PX4, 45, EL84, 7189 and 6V6GT single-ended amplifiers.

Suitable applications

• 2A3 and PX4 single-ended triode amplifiers using approximately 3 kΩ
• EL84, 7189 and 6V6GT output stages using approximately 5 to 6 kΩ
• 45 and similar triode projects operating at lower idle current
• High-end upgrades for compact single-ended and desktop amplifiers

Technical specifications

Transformer type

Open-frame single-ended valve-amplifier output transformer

Core construction

Lundahl audio C-core with highly sectioned windings and a low-capacitance winding technique

Recommended primary DC current

60 mA at 0.9 T core flux density

Air gap

Δ/2 = 125 µm

Primary inductance

46 H for the 60 mA 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

Transformer capability at 5.6 kΩ

13 W at 30 Hz with approximately 0.2 dB transformer loss

Transformer capability at 3.0 kΩ

25 W at 30 Hz with approximately 0.5 dB transformer loss

Transformer capability at 1.6 kΩ

50 W at 30 Hz with approximately 0.8 dB transformer loss

Power-rating note

These figures are magnetic transformer limits at 30 Hz and do not guarantee the amplifier's output power

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

Maximum primary signal voltage

270 V RMS at 30 Hz in single-ended operation

Thermal winding limit

210 mA at approximately 7 W winding dissipation; this figure does not replace the magnetic 60 mA operating point

Insulation

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

Dimensions

Approximately 118 × 85 × 78 mm

Weight

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

8 Ω using secondary alternative B or 16 Ω using alternative C

3.0 kΩ primary

4 Ω using alternative B, 8 Ω using alternative C or 16 Ω using alternative D

1.6 kΩ primary

4 Ω using alternative C, 8 Ω using alternative D or 16 Ω using alternative E

Valve-selection notes

For a 2A3 with a published load target of approximately 2.5 kΩ, the 3.0 kΩ connection provides a slightly higher and generally conservative load. For an EL84 or 6V6GT designed around approximately 5 kΩ, the 5.6 kΩ connection is also sufficiently close when the final operating point is verified.

The 60 mA rating is the intended magnetic maximum operating point of this air-gap version. Operation at a lower idle current is possible and is particularly relevant to 45, 6V6GT and other smaller output valves.

The open-frame transformer should be installed inside a closed chassis. Primary terminals and anode wiring require suitable insulation distances and effective protection against accidental contact.

Questions about choosing the correct SE output transformer

Which Lundahl output transformer suits a 2A3 or PX4 single-ended amplifier?

The Lundahl LL1623/60mA is a strong choice using its 3.0 kΩ connection for many 2A3 and PX4 operating points. A traditional 2A3 commonly operates at approximately 60 mA into about 2.5 kΩ, making 3.0 kΩ a moderate and generally conservative difference. A PX4 design should be checked against either the 3.0 or 5.6 kΩ connection.

Which high-end output transformer suits an EL84, 7189 or 6V6GT single-ended amplifier?

The Lundahl LL1623/60mA is well suited in its 5.6 kΩ configuration to many EL84, 7189 and 6V6GT operating points. These valves commonly use a primary load around 5 kΩ and approximately 35 to 55 mA of idle current. The slightly higher 5.6 kΩ load is generally conservative and remains within a practical matching range.

Is the LL1623/60mA suitable as an upgrade for an EL84 or 6V6GT amplifier?

Yes, when the existing amplifier is single-ended, requires approximately 5 to 6 kΩ and uses no more than about 60 mA of idle current. The 4 or 8 Ω secondary connection, mounting dimensions, feedback network, phase relationship and existing output level must be checked before installation.

Can the LL1623/60mA be used with a 45 or PX4 at lower idle current?

Yes, operation below 60 mA is entirely possible. The 5.6 kΩ connection is close to many traditional 45 load values, while a PX4 may use either 3.0 or 5.6 kΩ depending on its operating point. The lower DC current provides additional magnetic headroom.