Constellation - Talkback - Sudden high-pitch screech/squelch

For two weeks in a row, right before going live, our Constellation 2ME HD Atem switcher has been pushing out a high-pitch / high-frequency screech/squelch right before production starts over camera headsets and also to the talkback to the 4-wire interface to our Hollyland hub. Even after disconnecting talkback to the Hollyland, the high pitch/frequency noise continues to come out of the camera headsets, so it seems to be a long issue to the local to the Constellation switcher. I am posting to 1) confirm that it is not the "headset bridge interface" causing this issue, 2) to see if anyone has had this high-pitch / high-frequency issue over talkbalk/intercom before, and 3) ask for advice.

I have a headset bridge interface between the "Talkback" (shielded Rj45; double-4-wire) connection of the Constellation and the 4-wire connection of the Hollyland headset hub. This bridge interface has been working for a couple months, so the high / high-frequency noise is very odd.

Pinout guides:

• Hollyland's 4-Wire pinout (to XLR breakout): hollyland-techhelp.zendesk.com/hc/en-us/articles/7270355019155-Interconnection-Solidcom-C1-Syscom-1000T
• ClearCom's 4-Wire pinout does not connect the ground (gnd) for XLR:
  clearcom.com/DownloadCenter/manuals/EclipseHX_Delta_Online_Manual/Content/GPLTopics/Connecting%204-wire.htm
• Constellation "Talkback Pin Connections" is liTalkbalk pinoutsted on page 169 of the April 2024 switcher manual: documents.blackmagicdesign.com/UserManuals/ATEM_Constellation_Switchers_Manual.pdf?_v=1712905210000

Blackmagic - Hollyland audio bridge pinout table

blackmagic_hollyland_bridge_pinout_table.jpg (83.83 KiB) Viewed 685 times

Apologies: I was unable to post the table using phpBB code or html.

This sounds like you might be sending a Hyperdeck, Multiview or another video source that receives video and audio from the switcher back into the switcher, without enabling talkback mute for those video inputs.

The hyperdeck support 16 audio channels, so the intercom audio is sent to the hyperdeck on channes 13/14, 15/16. If you then send an output of the hyperdeck back into the switcher, the intercom audio is going to get sent in a feedback loop back to the hyperdeck, back to the switcher, back to the hyperdeck, back to the switcher etc. This will create a ramp up of increasing volume and pitch in the intercom lines until you can't wear the headsets at all.

If this is your problem, the solution is to use the built-in mute of the talkback channels for that video input (can be found in the Settings -> Audio-page I believe, but I don't have a switcher infront of me to create a screenshot).