USB DAC plays Windows system sounds but conferencing apps receive silent input on Windows 11

Environment

Dell XPS 13 9310, Windows 11 22H2 with monthly updates, external USB-A to 3.5mm USB DAC (Vendor: FiiO K3) connected via USB 3.0 port; conferencing apps tested: Microsoft Teams (Electron), Zoom (native), and OBS Studio. System sound playback and voice recorder produce audio output correctly.

Symptoms

When joining calls in Teams and Zoom, remote participants hear silence. Local microphone meter in Windows Sound settings shows no level for the USB DAC input during calls, but Windows 'Test mic' produces audible playback through the same device.

Observations

Windows Sound Control Panel and Settings show the USB DAC as default communication device; sample rate set to 48 kHz, 16-bit. Teams shows the device selected in its audio settings but displays microphone level at zero during an active call; Teams and Zoom both report 'no microphone detected' at times for the device. OBS can record from the USB DAC when using 'Run as administrator' but not when launched normally. Device Manager shows the USB audio device with no warning icons. Event Viewer log contains repeated 'Process: Teams.exe — cannot open device' warnings. Disabling 'Exclusive Mode' in device properties did not change behavior.

Already attempted

Installed latest USB audio driver from vendor; tried different USB ports and a powered hub; tested a different USB microphone (USB headset) — that device works in meetings. Reinstalled Teams and Zoom; cleared their cached settings; toggled 'Allow apps to access your microphone' in Windows Privacy; created a new Windows user and tested — same issue. Started apps as admin for OBS which allowed recording; running Teams as admin did not restore microphone in calls. Disabled enhancements and set default recording device explicitly.

Question

What additional diagnostics can identify whether this is an application permission/endpoint-sharing issue, a per-process access conflict, or a driver-level exclusive-mode lock? Which reversible steps will let me confirm the root cause without risking user data or prolonged downtime?

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AI DIAGNOSTICS

Incident analysis

Updated 1w ago• Trouble ID

Most likely causes

A driver or vendor utility running as SYSTEM or a different privilege level blocks non-elevated apps from accessing the device. 85%

One process is holding the device in exclusive mode preventing conferencing apps from opening the input stream. 70%

Conferencing apps are attempting to use an incompatible sample rate/format and failing to negotiate with the device. 15%

Summary

System playback and Windows test functions indicate the USB DAC hardware and basic driver are functional. The fact that a different USB microphone works, and OBS records when elevated, suggests a per-process permission or shared-access issue: either conferencing apps lack permission or a non-elevated process cannot access the device due to an exclusive lock by another process or driver-level policy. Event Viewer warnings about inability to open the device strengthen the hypothesis of access conflicts or per-process ACLs.

Suggested Fixes

Diagnostic step 1

Open Resource Monitor / Process Explorer and identify processes with open handles to the USB audio device (search for the device name or wave_*.sys). Reboot into safe mode and test whether apps can access the device (safe mode reduces interference from third-party drivers).

Diagnostic step 2

Temporarily disable vendor audio utilities and any system-wide audio processing services; reboot and test to see if conferencing apps regain mic access. These steps are reversible.

Diagnostic step 3

In Windows Sound Device Properties > Advanced, try toggling 'Allow applications to take exclusive control of this device' off for the input device and then restart conferencing apps.