Troubleshooting | Atmos sound dropping with Dolby CP850 ptp Grandmaster 00-25-90

Learn how to troubleshoot Atmos sound dropping issues when using a Dolby CP850 ptp Grandmaster with a 00-25-90 device.

Updated at June 8th, 2023

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Table of Contents

Affected Products

Hardware Model/Series Q-SYS Core and Dolby Atmos Cinema Processor
Software QDS


Audio sounds drop with a Q-SYS core and Dolby Atoms Cinema Processor. 


Audio drops with a Q-SYS core and a Dolby Atmos Cinema Processor are often caused by PTP Grand Master mismatch. 

Solution | Workaround

Dolby's CP850 and IMS3000 use Grand Master and are represented by a Dolby/Doremi MAC address. Under some circumstances such as reboot, these units show their vendor Mac instead and issue a few PTPv2 announcements. This causes the the core to lock to that Source. 

The tale sign for this would be a 00-25-90 Mac address in the core event logs.

For information on how to set up and troubleshoot Atmos systems with a Q-SYS Core, see the Q-SYS for Cinema Troubleshooting Guide in the Q-SYS help.