Order code: 1039
Hum loops and phase cancellations can occur as soon as the signal from an instrument is fed to more than one amp simultaneously. The one and only remedy for this is a high-quality transformer. Standard transformers modify the tone of electric guitars and basses very severely, since they are not designed to handle the low-strength high-impedance signals generated by instrument pickups. The LEHLE TRANSFORMER HZ, on the other hand, has been specially conceived for use with these high-impedance signals, preserving instrument tone and the interaction between instrument and amp and eliminating hum loops.
XLR Input
No Hum Loops
All LEHLE products not featuring a LEHLE TRANSFORMER HZ transformer and bearing this symbol switch the signal ground parallel to the signal itself via switches or relays with gold-plated contacts. Hum loops are thus effectively eliminated when switching backwards and forwards between different signal sources without, for example, simultaneous activation of two amps.
  • Isolator, Reamplification box and problem solver
  • Absolutely no signal loss or hum
  • High-impedance LEHLE TRANSFORMER HZ
  • Suitable for balanced or unbalanced signals
  • Passive – no need for a power supply

The LEHLE P-ISO XLR TRS combines passive isolation with the highest possible signal fidelity.
Its applications range from isolation and eliminating hum, to balancing and reamplification in recording applications along with any signal routing that requires a clean signal free from noise.
At its core is the high-end LEHLE TRANSFORMER HZ, which galvanically isolates the signal, eliminating any possibility of ground loops. The LEHLE TRANSFORMER HZ was specially designed for use with high-impedance signals but also processes low-impedance signals with uncompromising sound quality.
The classic application for the LEHLE P-ISO XLR TRS is as a reamplification box to eliminate hum noise and unbalancing of the signal. Frequently background noise caused by ground loops occurs when two grounded electronic devices are connected to each other.
The LEHLE P-ISO XLR TRS provides a simple, but extremely effective remedy when installed between the two units. By using the isolator, the devices are galvanically isolated and background noise becomes a thing of the past.
Thanks to its ability to use it in both directions and the choice of balanced or unbalanced processing, the LEHLE P-ISO XLR TRS is eminently suitable for many signal types and in numerous situations.
And just in case you are looking for a power connection: the LEHLE P-ISO XLR TRS performs all its functions without any need for a power supply. And due to its optimised size and low weight, it fits easily below your pedalboard or in any pocket.

Q: What is galvanic isolation?
A: Background noise, generated by ground loops, occurs again and again when two electronic devices are connected to each other, and the LEHLE P-ISO provides a simple but extremely effective remedy when installed between the two units. The two devices are electrically isolated when the 'A' output is used, eliminating this background noise.
The protective earth conductor and the ground connection of the audio signal create a loop which will pick up external interference generated, for example, by coils. Such interference will impair the signal. The LEHLE TRANSFORMER HZ transformer included in the LEHLE P-ISO galvanically isolates the ground connection. The hum loop is thus broken at this point.
Q: Does the galvanic isolation color my sound?
A: No, neither sound nor dynamics will be altered, the signal is passing the switcher without any loss in strength or frequency. We use our self-developed LEHLE TRANSFORMER HZ transformers for this, the selection of high quality components guarantees a rich sound throughout the full frequency range.
Weight 206 g
Length 71.5 mm / 2.8"
Width 49 mm / 1.9"
Overall height 34 mm / 1.3"
Frequency range 20 Hz – 100 kHz -0.1/ +0.4 dB (source 600 Ω, load 1 MΩ)
Total harmonic distortion 0.003 % (0 dBu, 1 kHz)
Input impedance (transformer load impedance) min. 2 MΩ at 2 kHz
Max. level 7.7 V RMS / 20 dBu (THD < 1%, 50Hz - 20 kHz)

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I have the following questions on the product LEHLE P-ISO XLR TRS (Order code: 1039)
Joachim Joki Schaller
Tel +49 2855 850070