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No Left Channel in bed when using Dolby Audio Bridge

This is a headscratcher.  I'd been using the Send/Return connection to the renderer for a large mix and decided it was time to move over to the Audio Bridge. My system (7.1.4) is calibrated and the renderer's speaker calibration window shows I get signal to all speakers. I set up the bridge as recommended by Dolby.

I then set up a very simple test session: 1 track for the Bed and another track with a mono object. On the bed track, I place a signal generator.  You can see in the meters on the Mix Window that there's signal on all channels.  But over on the Renderer, there's no signal in the left channel.  The signal looks like it got lost between Pro Tools and the renderer.  The attached graphic should make this clear.

But if pan the mono object all around the space, I get signal in the appropriate channels--even the Left Channel.

I've attached the graphic and also the session.  I'm curious if anyone else has run into this.


Thanks Fin.  No headphones plugged on or out. My system is native, so the output driver is set to my Focusrite Thunderbolt interface.

It may be as simple as a lose thunderbolt connection, or a manual change to the device. Open prefs, reselect Focusrite device, and this will clear the error. 

Might be, but that's extremely unlikely.  The interface works all day--except when I try to use the Audio Bridge--and it's always there, connected and running when I look right after this failure.

Hmm, interesting. Please let me know if it happens again, and if you can get the log files from when it happens that may help shed some more light on the reason.

Thanks very much Fin.  I'll do just that.  Have a good'n.

Hi Michael,

One other thing to check.  In the Rednet App settings for the Focusrite 16Line it is switchable between Pro Tools and Thunderbolt.   Can you verify it is in "Thunderbolt" mode and not "Pro Tools" mode using the Digilink connections?  I don't have one in front of me but I believe it will still show up in the Renderer audio output device list but not function properly if left in "Pro Tools" mode.


Sorry I was away for a few days--stuff to do.

I think I understand the problem.  It appears that on a fully native system, I can't use Audio Bridge for more than 32 objects (unless I spring for a Digilink license).  Even in that case I can only get a max of 64 objects.  It appears the only way I can use the full channel count of Audio Bridge is to have 2-HDX cards!  This is a pretty expensive solution.  I think the error message I've been seeing is because Audio Bridge expects 128 output channels (even if they're not really going outside the box) and the HD Native limitation is 32 channels.  So it sure smells like I'm going to have to go back to the Send/Return method.

Does this analysis make sense to anyone?

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