40 dBFS hiss at end of loop [solved: ZynReverb is bad, ardour is good😋]

Hi y’all,
i’m getting a 40 dBFS hiss randomly at the end of a loop.
(OS: Manjaro Linux x86_64, Kernel: 6.4.6-3-rt8-MANJARO, ardour 8.1-1)
the hissing ends after some seconds. I’v only four short midi tracks which play dexed.

i’v managed to record a video of the bug (?), but without audio: https://youtu.be/agZOSgf_zlg

the video shows, that none of the virtual instruments is responsible for the loud hiss, but the master mix is at full level.

Thank you for all help.

Try disabling ZynReverb on the master bus. When a bus gets stuck at maximum level it usually implies there is feedback somewhere. You can check the connections window to make sure the output of the master bus is not connected back to anything which could be an input to the master bus, but reverbs can get feedback loops as well (either from poor quality code/design or settings not limited to usable ranges).


While searching for ZynReverb I see that there have been a couple of bug reports of ZynReverb crashing Ardour. Looks like it may not be the highest code quality.

As an aside, a more typical connection scheme for reverbs is a separate reverb bus which feeds into the master bus. Set the reverb on that bus to 100% wet/0% dry signal, and then you can easily control the reverb level with the fader on the reverb bus. Use sends from individual channels to send individual tracks to the reverb bus, and you can have rudimentary control of depth perception by controlling the reverb send (less send to the reverb bus makes the sound “dryer,” which gives an impression of closer, more reverb send gives an impression of farther back into the stage).


thank you very much!
yes you were right, »ZynReverb« was the source.
thank you for the hint with the seperate reverb bus.

don’t know why i choose ZynReverb, usually i use Aether, Dragonfly Room Reverb or Delay Architect…

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