LL1588 Lundahl Line Übertrager high level - low imdedance

Lundahl LL1588 high-level line and studio transformer

The Lundahl LL1588 is a high-level 1:1 audio transformer for professional line and high-quality hi-fi applications. It supports galvanic isolation, XLR/RCA conversion and passive phase splitting ahead of a push-pull stage.

Its dual-coil construction, electrostatic shields and mu-metal enclosure reduce sensitivity to external fields from mains transformers, motors and power supplies.

Suitable applications

• High-level DAC, studio and preamplifier signals
• Galvanically isolated line input or DC-free line output
• Passive phase splitting for push-pull valve stages
• Balanced and unbalanced audio interconnections

Technical specifications

Transformer type

High-level line, microphone and isolation transformer, one channel per component

Winding arrangement

1 + 1 : 1 + 1

Core and enclosure

High-permeability mu-metal core in a mu-metal can

Winding construction

Symmetrical dual-coil design with electrostatic shields

Frequency response

10 Hz to 100 kHz within ±1 dB using a 150 Ω source and 10 kΩ load

Phase response

Deviation from linear phase within approximately ±0.5° from 20 Hz to 20 kHz

Level and distortion in series connection

0.1% at +25 dBu or below 1% at +28 dBu and 50 Hz

Self-resonance

Above 250 kHz

Insulation

4 kV between windings and 2 kV between windings and shields

Dimensions and weight

Approximately 47 × 28 × 24 mm and 115 g

Mounting

PCB mounting with 5.08 mm pin spacing

Connection and operating notes

High-level isolation

Series-series 1:1 connection

Low-loss isolation

Parallel-parallel connection for low-impedance sources

Phase splitting

Symmetrical secondary halves provide two opposite-phase outputs

Line output

The signal must be DC-free; use a coupling capacitor with an active stage carrying DC

Questions about choosing a high-level audio transformer

Which Lundahl transformer suits a high-level DAC or studio output?

The LL1588 is a suitable choice for low-impedance sources and high line levels. In its series connection, the documented test gives +25 dBu at 0.1% distortion and 50 Hz, with response extending to 100 kHz within ±1 dB from a 150 Ω source.

Which transformer can provide passive phase splitting for a push-pull valve stage?

The LL1588 can divide one input into two symmetrical opposite-phase secondary signals. Its documented phase deviation is no more than approximately ±0.5° from 20 Hz to 20 kHz. The following valve circuitry should present a sufficiently high load.

Can the LL1588 interrupt ground loops between studio or hi-fi devices?

Yes, its galvanic isolation removes the direct signal-ground connection. Connectors, cable shields and chassis grounding must be arranged so that primary and secondary returns are not rejoined elsewhere.

Is the LL1588 a higher-level upgrade from the LL1527?

Yes, when the system requires greater line-level headroom, a low-impedance source and very wide bandwidth. The LL1588 is larger and handles higher levels. The LL1527 remains more economical and flexible for general isolation, 1:2 microphone matching and simple splitting.