1
Diagnostic step 1
Back up all Logic Pro projects before further tests. Avoid destructive changes to audio files during diagnostic testing.
FULL AI ANALYSIS
Audio dropouts with external USB interface when connected through Thunderbolt dock while laptop is charging
Generated Oct 3, 2026, 12:35:03 AM
Analysis summary
The logs showing USB device disconnect/reconnect alongside dropouts and the direct-connection success point to the dock or Thunderbolt link introducing transient USB host resets, likely during PD or link re-negotiation. Possible contributory factors are cable quality (not full TB4 spec), dock firmware bugs handling USB device power, or power draw anomalies when the internal battery is charging via the dock. CoreAudio treats device re-enumeration as device removal which can cause underruns and audible glitches.
Possible causes
Thunderbolt dock firmware or USB controller firmware causing USB device re-enumeration on power negotiation or load changes.
85%Dock power delivery events (voltage/current changes) triggering hub resets on the dock.
80%Thunderbolt/USB-C cable not rated for full TB/USB host power and data stability, causing intermittent disconnects under PD negotiation.
60%Driver or CoreAudio handling of device re-enumeration leading to underruns in low-latency audio workloads.
50%Suggested fixes
2
Diagnostic step 2
Reproduce the issue with logging enabled: capture Console logs (filter for IOUSBHostDevice and IOAudioEngine) while reproducing a dropout to get precise timestamps. Note whether PD negotiation occurs at the same time (Console may show related messages).
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Diagnostic step 3
Test with a Thunderbolt-certified cable known to support required PD and data rates; compare with a verified direct TB4 cable to rule out cable limitations.
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Diagnostic step 4
Use the direct connection to the Mac as a control test — if it consistently eliminates dropouts, the dock is the likely source. Try with a different dock if available.
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Diagnostic step 5
Temporarily set a higher audio buffer size in Logic while testing to reduce underruns; do not overwrite original project files — use duplicates when testing settings that modify audio files. If the dock is implicated, contact the dock vendor with logs and request firmware guidance; escalate to Apple if kernel logs show device driver level disconnects that persist across docks and cables.