Hi all,
I have a FiiO K5 Pro connected one of the USB3 ports on my primary system, running Ubuntu Jammy. I have so far been unable to isolate a persistent problem with audio playback, and I am writing to you all in the hope that maybe someone on this mailing list might have experienced (and solved!) the same problem.
I work in IT and have thirty years of using Linux as my primary OS. I'm confident that I can solve any audio-related configuration issues on my own, but what I have been unable to do so far is definitively correlate what I hear with a kernel module or software package. I am pretty certain that if someone has had the same issue as I have, they will know what I am talking about simply by a description of what I hear.
When I have audio playing (normally music) there are irregular noises that sound at times exactly like a turntable stylus hitting a scratch or two (but not repeating), and at other times almost exactly as if someone has bumped a turntable - a slightly longer sound with a stuttery aspect to it. If you've ever been to a nightclub where they are playing vinyl you will know the sounds I am talking about. The music is not interrupted or distorted as far as I can tell - though I wouldn't be surprised if there were timing deviations that I can't pick up from just listening.
I hear these sounds irrespective of whether I'm using mplayer, vlc, or playing video, etc. The noises are irregular as I said, happening one or two times a minute. They are not tied to the sound being played, which is to say I can play the same music file and the noises will not occur at the same timestamps. Nothing is reported by the applications (incl. with debug settings), in the dmesg output, or anywhere else.
I am fairly sure that the problem has something to do with the snd_usb_audio kernel module, but I have tried both standard and non-standard module options (quirk flags) to see if I could influence what is happening. Whatever is causing it, the problem has persisted through OS upgrades and the switch from Pulseaudio to Pipewire.
What I really hope for is for someone who recognises the specific problem I describe and knows precisely where I should be looking for a solution. I haven't found any similar reports though, so I concede that the chances of someone actually having come across this before are probably pretty slim, but no harm in asking, right?
The FiiO K5 Pro has a XMOS XUF208 for USB decoding, and a AK4493 DAC. I haven't entirely ruled out a hardware problem, but I can tell you that I hear the same disturbances when the K5 is used with other Linux systems as well. I have yet to test it with Windows, partly because I'm terrified that it will just work flawlessly!
If you think you know what might be going on, please let me know. If you haven't come across this problem before yourself, but have some tips on how I might better articulate the problem, or if you could suggest strategies for how I might make some headway in diagnosing the problem, I would love to hear from you.
Many thanks,
Paul Dorman
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