LDR Optocoupler Hi-Fi Attenuator - Technical Data & Laboratory Tests
Intermodulation Distortion Test
The IMD at medium volume for 01 Hz - 20 kHz, the attenuation here is around -20 dB, there are no disturbances in the spectrogram for all the time of the test that is above the noise level. If any IMD is present is well below the noise and not audible.
The IMD at -40 dB for 01 Hz - 20 kHz, some very small disturbance at low frequency appears slightly above the noise floor. We are talking here of very low listening volumes, nearly the noise floor of a well sound-insulated room in a quiet suburb.