Audio line isolator

The ALI20/25 are audio line isolators designed to isolate audio devices from each other. In most cases, they are used to avoid hum caused by ground loops in audio systems. They offer a complete passive solution for the isolation of a stereo balanced audio signal. It features dual XLR in- and output connectors and a ground lift switch. The in- and output phase are matching. The ALI20/25 are both built with an audio transformer that has a turns ratio of 1:1 and an impedance of 600 Ohm. The difference is the shielding of the transformer. The ALI20 contains a shielded transformer which complies with the requirements of most standard applications, while the ALI25 contains a MU-metal shielded transformer which can be used when regular shielding becomes inadequate. This ensures the best results in even the highest EMI polluted environments.


  • New ALI20MK2 - Shielded
  • ALI25 - Super shielded
  • Discontinued ALI20 - Shielded
    Replaced by ALI20MK2
System specifications
Turn ratio 1 : 1
Bandwidth 0.8 Hz - 100 kHz
Typical distortion (@ 1 kHz) 0.001%
THD+N (@ 1 kHz) 0.035% (@ 20 Hz and -20dBu (typical))
< 0.001% (@ 1 kHz and -20dBu (typical))
Inputs Impedance 600 Ω
Connector 2 x XLR female
Outputs Impedance 600 Ω
Connector 2 x XLR male
Frequency High -3 dB Cutoff 105 kHz
Low -3 dB Cutoff 0.8 Hz
Response 20 Hz -0.09 dB (reference 1 kHz)
20 kHz -0.10 dB (reference 1 kHz)
Max. Inputs Level (@ 1% THD+N) 20 Hz +2 dBu (0.975V)
50 Hz +10 dBu (2.449V)
Product features
Dimensions 96 x 43 x 108 mm (W x H x D) (ALI25)
108 x 44 x 165 mm (W x H x D) (ALI20MK2)
Weight 0.270 kg (ALI25)
Colours Black

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