builtin sound: frequency distortion

[asheplyakov]

Steps to reproduce:

1. Connect speakers (or a headset) to the builtin audio output
2. Play 440 Hz sine wave (for instance from https://www.youtube.com/watch?v=xM6cFKJRl4s)
3. Record the sound on another computer, measure the frequency with a (software) tuner (such as https://github.com/ibancg/lingot) or oscilloscope

• Expected result: measured frequency is 440 Hz
• Actual result: measured frequency is 468 Hz

[ValdikSS]

Hardware issue, likely won't get workaround in software.