Echo when live streaming a video from computer

[Stevo2025]

We arehaving a issue with our church system. We use a MacMini that host the OBS. it also uses Castr and sends out live stream to Youtube and Facebook. If we try to play any audio/video from the Mac it creates an echo in both the online stream and local in the church building. The Mac has an output to the sound board and the sound board feeds a combined signal back to the PTZ camera input that feeds to the OBS on the Mac. I assume since the "original" sound source is the Mac, and the OBS "output" is also coming from the Mac this is creating the echo. I actually heard the OBS output from the Sound board this week. Is there a way to separate audio from OBS for the streaming apps and the sound board? I can't mute the computer since that is the video source.
Any ideas are appreciated. I am the sound guy and other have the knowledge of how the streaming side works.
The response below was checked and the default is disabled on both system and option. So starting a thread here to seek more ideas.

From AaronD:
Anyway, OBS comes with both a Desktop Audio capture and a Mic/Aux enabled by default, and both set to "Default".
Settings -> Audio

The "Default" setting follows the operating system's choice of device to connect to, which can and will change at some point, which will very likely break your rig without warning. So you should change everything away from "Default", if you haven't already. Choose a specific device instead, or "Disabled". Don't ever have anything set to "Default", unless you have a very good reason to actually want that automatic device-switch.

If you have a final, finished soundtrack coming in from somewhere else, then you should delete or Disable everything else. Don't keep stuff around that can only hurt.

If you're still having problems after those two points, start a new thread on the Mac side.

 

[AaronD]

Another possibility is a feedback loop in the sound board itself. I've made one on purpose with a single-shot delay effect to create a repeating delay, instead of having the FX unit do the repeat. Slightly different workflow that way. Essentially, feed the FX unit from an Aux send and return it to a full channel strip, so I can then send that channel strip to the same Aux. Be careful to not have that send over unity, or the repeated echo will increase rather than fade away, but it otherwise works about like you'd expect.

If you're doing that with OBS instead of an FX unit (probably by accident), then that might be your problem.

If you want OBS to have a copy of what it sent to the board, then you'll have to stop OBS from sending *that* back to the board. Go to the Advanced Audio Properties, uncheck the Active Only box at the bottom left (don't know why it's even there, especially since it doesn't remember the correct setting so you have to fix every time), and make sure that the feed from the sound board is set to "Monitor Off". That Monitor is probably the feed to the board.

As above, I'd recommend setting the feed from the board to "Monitor Off", and everything else to "Monitor Only". Then the stream and recording only have what comes from the board, and everything else must go through the board to get there.

 

[AaronD]

Yet another possibility is that the Mac OS itself is echoing the audio input back to the board. If that's the case, then it would do it even when OBS is not running.

I'm not a Mac guy - formerly Windows from about mid Win10 and before, and switched to Linux when I got fed up with it - so I can't tell you where that setting would be. Windows calls it "Listen to this device", and it's buried deep in the settings for each input.

 

[Stevo2025]

Seems like it was in OBS. We had both a screen capture input and the camera input. That created the echo. We muted the screen capture audio and the echo is gone. We’ve done a couple computer based video feeds since the change and no echo.