Up front: I continue to realize what a cute little thing the RU6 is, most of all soundwise and what has been packed into this small form factor. But I keep coming across some gotchas…
I would like to give an initial report here on my findings with the RU6 and Linux when I feed it from a Linux laptop via USB-A > Cayin USB-A to C > Cayin USB-C to C cable. I am using openSUSE Tumbleweed for now, which is a rolling release distro with everything updated to their latest versions. I did already mention here that I prefer to have the audio player software play directly to alsa in order to ensure bit-perfectness; that means any pulseaudio or pipewire is bypassed. My audio player software are the ”audiophile standard“ mpd+Cantata (Music Player Daemon service with Cantata as graphical control interface) and DeaDBeeF (stand-alone player, similar to foobar2000 on Windows). For your reference, there was a website by Ronald van Engelen (lacocina.nl), which unfortunately is defunct now, but accessible through the wayback machine - this site taught me the basics of audiophile Linux.
As is well known, there is no need for ”external“ (manufacturer-supplied third-party stuff) audio drivers under Linux, since alsa with its kernel modules takes care of talking to the hardware (if it can). My Linux systems (both Tumbleweed as well as Manjaro, the latter not tested with the RU6 yet) work flawlessly out of the box with all my USB-DACs, Chord Hugo 2, Cayin N6ii, and AudioQuest DragonFly Red; EDIT: same for the miniDSP USB-to-optical Streamer.
Unfortunately, I do have a mixed bag of findings to report with the RU6. Most of the time, everything works fine, but there are occasional glitches of various kinds. I’ll restrict myself here to playing PCM from local FLAC files, all standard bit depth / sample rates (BD/SR for short).
What is happening?
(1) When two consecutive tracks have identical BD/SR, playback works fine all the time.
(2) However, when one or both of SR and/or BD change from one track to the next, a failure can occur right from the start of the second track - loud ”white“ noise, which supposedly continues for the entire track (the track time display progresses, but I stopped replay at some point, of course). Such misbehavior occurs with both player apps tested, in identical ways.
(3) I couldn’t find any systematics yet for that gross misbehavior:
(a) It does not occur at all SR/BD changes.
(b) It occurs both when the gapless player apps transition from one track to the next, as well as when I start the second track myself while playing the first one.
(c) When I have encountered a misbehaving track sequence, then the misbehavior is reproducible most of the time, but sometimes not.
All that is so very strange.
@DBaldock9: We both do observe that an error occurs at a SR/BD change. But you got a hang-up when using pipewire / JRiver, which I never got up to now. I just get this loud white noise.
@DBaldock9: What is your status now, please?
Let me mention again: I don‘t encounter such a gross error with any of my other USB-DACs listed above, when I use them one at a time. Moreover: One can set mpd up to play to several USB-DACs simultaneously, each one hooked up to different USB outputs. Guess what: Only RU6 produces white noise, while any other USB-DAC continues to play properly simultaneously.
And: On a Windows system, my RU6 is well behaved, mostly (cf. above for my issue with Roon & ASIO).
In summary, I get ”white noise“ at some SR/BD changes under Linux. Unfortunately, I am still clueless as to any systematics. I will keep on after the weekend and report back.
YMMV.
