I am attempting to eliminate possible poor electrical connections associated with the headphone socket by starting up the laptop from cold (literally having cooled down) and running a video to check the sound quality.
Last evening, within 10 minutes of starting the laptop from cold, the sound became crackly. I used the Test Sound button on the Sound panel and found no response from the Front Left Test button. However, the Front Right Test button caused a muted response from the left speaker! I did an immediated restart and everything then worked perfectly - no crackles and correct sound tests. This morning, after an overnight cold soak, the system started up and the speakers responded correctly to the Test Sound button. However, within 10 minutes of playing a video, the sound became crackly. The speakers responded correctly to the test Sound button and the crackles subsided. I plugged in a pair of headphones which caused the device identification panel (headphones, headset or microphone) to pop up. However, the sound was directed through the headphone straight away. On removing the headphones, the sound went back to the speakers without having to click their menu item in the Sound panel. (Has the system "learned" from previous connections?) After a further 20 minutes of playing the video, the sound became crackly again. The speakers did respond correctly to the Test Sound button but the crackles were still evident. I picked up the laptop and gently tapped the underside of the case near the headphone socket. This might have contributed to the crackling sound but it then disappeared and the speakers sounded normal again. By this time, the laptop had warmed up to its normal operating temperature. Since plugging in headphones seems to cause an interrupt that brings up the device select panel, there must be an electrical interface between the headphone socket and the circuit board. I doubt if the headphone socket is gold plated but intermittent connection must be expected with such an interface. Normally, when there is a connection between mechanical contacts and electronic circuits, some form of bounce suppression is employed. Apart from the early electronic calculators that used mercury wetted reed switches, it has been common practice to include this bounce suppression in the software. I am sure that this has not been overlooked in the Linux kernel but it might be prudent to ensure that such a bounce suppression is compatible with the cheap and chearful electrical contacts found on headphone sockets. (Software bouce suppression works well enough on keyboards. Perhaps the parameters used could be migrated to the headphone socket interface.) -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1402666 Title: [XPS13 9333, Intel Haswell HDMI, Digital Out, HDMI] Playback problem To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1402666/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
