Context While playing YouTube videos in Firefox, intermittent crackling appears after a few minutes of playback. This report documents detailed testing that demonstrates the issue is not related to the DAC, USB interface, or system hardware, and is exclusive to Firefox. 2. System Configuration CPU: AMD Ryzen 5 5600X @ 43 °C RAM: 64 GB DDR4 dual-channel (16-20-20-38 @ 1572 MHz) Motherboard: ASRock X570 Phantom Gaming 4 (AM4) @ 54 °C GPU: NVIDIA GeForce RTX 3050 (audio drivers disabled, audio hardware off) Monitors: LG HDR WFHD 2560x1080@60Hz and IPS236 1920x1080@60Hz Storage: Multiple SSD and HDD SATA drives (500 GB – 2 TB) Audio: Realtek High Definition Audio disabled; iFi nano/UNO DAC connected via USB with power filtering, using Exclusive Mode / ASIO 3. Tests Performed 3.1 DAC and USB Validation Continuous playback of PCM 384 kHz/24‑bit and DSD256 via Roon/ASIO. Duration: over 25 minutes of uninterrupted DSD256 playback. Result: no crackling, pops, or errors. Conclusion: DAC, firmware, USB cables, ports, and power supply are fully operational; heavy data load does not cause errors. 3.2 Browser Comparison Chrome (YouTube, identical conditions): continuous playback without crackling. Firefox (YouTube, identical conditions): crackling progressively appears minutes into playback, temporarily disappearing when the video is paused. 3.3 Isolation of Variables USB motherboard ports and original drivers fully tested. GPU audio drivers and hardware disabled. Windows Shared Mode off, Exclusive Mode enabled. Predefined audio formats set according to DAC preferences. USB power management disabled. DAC temperature stable; no overheating observed. 4. Technical Conclusion Hardware: DAC, USB, cables, power, firmware, and GPU are not the cause of the crackling. Operating System: Windows 11 is correctly configured; Exclusive Mode / ASIO works without errors. Browser: Firefox is the only element consistently reproducing the issue. Most Likely Cause: Firefox’s buffer management and audio sandboxing interacting with Windows, causing intermittent interruptions in audio flow. Summary: All hardware and OS factors have been tested and validated: DAC, USB, cables, power supply, firmware, GPU, and temperature do not produce crackling. The only consistent factor is Firefox, making this a software-bound issue. Engineering Note: This diagnosis conclusively demonstrates that the intermittent audio crackling on YouTube is caused exclusively by Firefox on Windows 11, independent of DAC or USB hardware. The issue should be investigated at the browser level, specifically how Firefox handles continuous digital audio streams and buffers on Windows.