Apple has not fixed the macOS audio left/right balance bug for nearly 10 years

Original Article ↗ Hacker News Discussion ↗

Apple users report a long‑standing macOS bug where the system’s left/right audio balance can drift unexpectedly, often when changing volume under high CPU or memory load, and say it has persisted for more than a decade despite workarounds like third‑party “balance lock” utilities. Commenters describe related audio issues such as crackling, device disconnects and Bluetooth quirks, contrasting these with macOS’s reputation—and continuing reality for many—of having a more reliable audio stack than Windows or Linux. The thread broadens into criticism of Apple’s bug‑fixing priorities, lack of a transparent bug tracker, and a perceived shift from “it just works” polish toward tolerating long‑term usability problems, especially when non‑Apple hardware or less profitable usage paths are involved.

Overview of the macOS L/R Audio Balance Bug

  • Bug: System audio balance drifts left or right over time, sometimes visibly moving the balance slider.
  • Apple’s own old KB (via archive) said it can happen when rapidly pressing volume keys under heavy CPU load.
  • Some report it mainly with built‑in outputs or certain USB/Thunderbolt docks and DACs; others with Bluetooth devices or AirPods.
  • Many have never seen it despite years of heavy audio use, leading to debate over how widespread it is.

Hypotheses and Technical Speculation

  • Suggested cause: volume-up/down implemented per channel; under high load one channel update is dropped, causing imbalance.
  • Others mention race conditions between the OS and Bluetooth devices, or unreliable per‑channel commands over USB.
  • Another angle: mismatch between UI abstractions (pan/gain) and underlying per‑channel hardware controls.
  • Some argue proper retries or better CoreAudio design should mitigate dropped commands; others point out complexity similar to distributed state sync.

Workarounds and Third‑Party Tools

  • Multiple users rely on “balance lock” utilities (free and paid) that monitor and reset balance to center.
  • Some resort to external DACs, optical outputs, or exclusive‑mode audio in apps to avoid OS mixing issues.
  • Others report that recent macOS versions appear to have reduced or eliminated the issue for them, but not universally.

Broader Apple Audio and OS Reliability Complaints

  • Numerous reports of crackling, pops, device resets, USB audio dying until unplug/replug, and glitches under memory pressure.
  • Some attribute glitches to real‑time audio pages being swapped out; test code is cited that shows glitches rising with memory pressure.
  • Other recurring issues mentioned: Bluetooth profile switching, slow‑motion or sped‑up audio/video, wake‑from‑sleep problems, and long‑standing UI/UX quirks.

Apple Quality, Incentives, and Comparisons

  • Many commenters see this as emblematic of Apple tolerating long‑standing bugs, especially on “non‑golden path” use cases (third‑party hardware, non‑Apple services).
  • Some defend macOS, saying CoreAudio still “just works” better than Linux (Pulse/PipeWire/JACK) or Windows (WASAPI/ASIO) for production work.
  • Others argue macOS is now merely “slightly better than Windows,” with hardware quality outpacing software polish.

Meta: Bug Reporting and Responsiveness

  • Several note Apple’s opaque bug reporting (“black hole”) and lack of public tracking.
  • Others report positive experiences when working directly with Apple engineers, but acknowledge that public pressure often moves the needle more than detailed reports.