Input channel Listen mode with Direct Monitoring = loud phasing sound

Tested with Nuendo 8.2 and MR816csx interface :

When using the Listen button on an input channel (ASIO direct monitoring enabled) Nuendo forget to mute the channel output.

Nuendo mix the direct monitor sound (the source signal routed directly to the monitor bus by the interface dsp mixer) with the sound from the Nuendo input channel sent to the monitor bus !

This create a loud phasing sound with around 3 dB more level than we should have.

Very surprising…

I do not think that this is a hardware control problem, just a mute management problem when ASIO direct monitoring is enabled. Nuendo should mute the input channel routing to the listen bus when clicking the Listen button. And it does not do it.

how to reproduce :

  • create a Nuendo input channel

  • connect an audio source to the audio interface on this channel

  • check that ASIO direct monitoring is enabled in vst audio device preferences.

  • click on the listen button in this input channel. You should get the audio interface sending the corresponding input directly to the monitoring channel. You will get at the same time the sound coming back from the Nuendo input channel, creating a surprising phasing and level rise compared to the level you would have in the mix through an audio channel.

    To prove that the phasing does come from a mix between the direct sound and the Nuendo channel sound do that :

  • set the Listen level to 0 dB and the listen DIM level to the minimum (settings available in the expanded “main” area of the control room)

  • put a test generator vst plugin on a insert slot in this input channel and enable it with the default sine signal.

  • when listen button is not enable, you should not ear anything.

  • when listen button is enabled, you should ear both the direct monitor sound (the source input signal connected to the audio interface) and the Nuendo input Channel signal.

This is not normal here. Nuendo should mute the channel signal.

  • now try to enable and disable the test generator. You will ear the input, with or without the test generator. This prove that Nuendo forget to mute the input channel output to the listen bus, when switching the audio interface to direct monitoring for the listen function.

  • to compare the levels, create an audio track using this input and set it’s fader at 0dB.

  • disable the generator on the input channel.

  • disable listen button on the input channel.

  • click the monitor button on the audio track.

  • here you should listen to the input channel at 0 dB level unmodified level.

  • now click the listen button on the input channel : you will ear the level rising, between probably around 4-5 dB. Should be 6 dB but the two signals are not in phase. So this is certainly a bit less than 6 dB.


  • last : disable ASIO direct monitoring and redo those tests. The problem disappear.