• TR62
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Topic: Ubuntu + UFX + Reaper

Hi All,

On Win10Pro, Reaper, UFX, USB connection, I am able to use 64sample buffers, which is very useful for live keyboard playing into Reaper, with both h/w synth and VST layer elements to the sound/MIDI recorded.

Somewhat unimpressed by Microsoft's TPM/Win11 proposition, and before spending £1000's on new hardware just to suit TPM, I thought I'd install a new 2Tb SSD, and make a serious attempt to move to Linux. 

I chose Ubuntu25.10, without any motive aside from it seems to be mainstream, and lacking ANY prior experience with Linux.  My logic is that it is the Linux Kernel on test, rather than any specific distro.  Provided it has RT potential, that should be basis enough.

To summarise a couple of days of this test, Ubuntu25.10 easily and competently replaces Win10 for office, email, browser, network, printer.  I have access to all my old files, once mounted.  VSCode, Reaper, Signal, GnuCash all load easily enough, either from App Center, or running .sh scripts.  Audio less so.

The more challenging things, like installing a newer version of Wine, are a struggle, if simply following the instructions at WineHQ - they are out of date, or perhaps incomplete.  I got errors about keys, out of date commands, and so on.  So here I figure is where someone more experienced in Linux would have done better.  I do not mind the learning curve, but it would be helpful if the how-to notes were correct!  I will likely come back to Wine, and Yabridge.

Now, I would have thought, if the original Win10 SSD is mounted, reinstalling VSTs would be pointless, and Wine mght be able to simply point at the files on the original Windows SSD?  Jury is out.  Every tutorial I have seen, naturally, expects you to install the VST again.  Small price to pay for not losing the whole VST estate I suppose, but we have over 650 of them to move, if so.  If someone has done this - or thinks it's possible - that would be useful info.  Maybe it needs reg keys recreated as part of the install.  Who knows.

Crucially to this forum, the UFX (a mk1) was set to Class Compliant mode (CC mode), and provided 22x22 channels, although Ubuntu does not let you choose the correct pair of said 22 for audio out under ALSA at least, so, YouTube video audio (for "how to" resources) were sent to a VDU speaker output.  It worked for that. 

In Reaper, things were more hopeful.  All 22 ins and outs were listed under ALSA.  It is very similar to the Win10 version in most regards, although I seriously miss the convenience of ASIO and all 30x30channels.  Half my connected audio kit is missing - I am using both ADAT ports for line in/out to rackmounted gear.  One ADAT unit's I/O is simply inaccessible in Reaper.

The low point for me is that the audio buffers have to be a huge 256samples, compared with Win10's 64samples.  There is something called "periods" in there as well, and I have little notion of what is best at this stage of the game.  It produce high pitched digital tones when it messed up the audio. 

v7.52 of Reaper seems to have some nasty UI bug with menus freezing - the forum there shows others experiencing this.  Bugs acknowledged.  One version to avoid.

So, my conclusion, is that in the absence of an RME kernel audio driver, Ubuntu underperforms compared with Win10.  I miss the control panel (Total Mix UI) because I use the submixes and matrix a lot, and run OSC commands to it, using OSCii bot. 

However, I am not persuaded by Microsoft and Win11 at all, so appear to be at an impass.  Never has something so offensive provided more motivation to jump ship.  Hence, I shall likely move all office/text/code to Linux, and only remain do audio on Win10, for the lack of an ASIO-esque driver suited to the main RT Kernel.  How ironic, that it is for the want of a high performance audio driver, I cannot completely make the jump to Linux - and that is the ONLY reason, at least for my PC usage, with the studio/live/business.  Not a rant, just piqued!

I would be most interested to know if other people can get better buffer settings working.  That would help.

I would also like to know what potential the mainline RT Kernel has for future drivers - could Linux achieve the same performance as Win10 theoretically?  Or is ALSA just not performant / yet?

Perhaps it would help to vote up one RT Kerrnel to play with as a community, irrespective of personal distro preference, as a test bed in such things.  But, then I am new to Linux, and this is for more capable users to chime in.  Here to learn.  What's your thought?

2 Reply by TR62 (edited by TR62 2025-11-27 17:42:00)

  • TR62
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Re: Ubuntu + UFX + Reaper

This may help someone looking.  Edit "/etc/defaults/grub.d" to get RT performance from the generic Ubuntu kernel:

    • preempt=full    Makes the kernel fully preemptible
    • rcu_nocbs=all     Offloads Read-Copy Update (RCU) callbacks from all CPU dedicated to kernel threads, improves real-time performance
    • threadirqs         Forces interrupt handlers to run in a threaded context, reducing buffer xruns

These are the tweaks made in Ubuntu Studio.

Interesting that Pipewire is boasting the 64sample buffers and low CPU usage I am seeking, so I shall try modding Ubuntu to use this next.

In the PowerPoint presentation about Pipewire, there is a "H/W DSP node (assuming interface implemented)" described on a slide explaining Pipewire, which draws immediate comparisons to ASIO.  So saying, could that make a good starting point for considering a high performance driver for a hardware device?  Maybe theis Pipewire "node" interface is the "ASIO of Linux"?
The slides are here: https://wiki.automotivelinux.org/_media … 181206.pdf

  • From: Germany
  • Registered: 2025-02-06
  • Posts: 34

Re: Ubuntu + UFX + Reaper

From a lot of testing lately with various PC hardware and RME devices, old and new, I can tell that OS settings play a very small part. It could be a different story with DAWs and lots of plugins, but basic output and roundtrip-latency are unaffected, at least I remember no dealbreaker setting or better or worse distro.

Pipewire I would say is a double-edged sword. It is awesome when "desktop audio" is needed (and for the most part, sooner or later it is) but I've come to uninstall it for a more raw and consistent configuration with Jack only, on a pure audio workstation.

It seems odd to me that the UFX can't go below 256 samples. Maybe you can try it on newer hardware once and with a resource insensitive tool (like jack_iodelay from jack-example-tools, just run it and connect the in and out it in qjackctl graph and on the device, then gradually decrease sample rate from 256, to 128, to 64)

Maybe a Firewire PCIe card and FFADO is the cheapest way going forward with your current hardware. Or you could find a mixed solution where you get one new, fast interface like the BBF Pro FS for live playing (and you could still hook up 8 Channels via ADAT to the UFX or other outboard gear) or one of the native PCI/PCIe solutions that work with hdspconf/hdspmixer like AIO or Multiface.

UCX II, BBF Pro FS, Quadmic II, PCIe HDSPe Multiface II, AIO Pro

4 Reply by TR62 (edited by TR62 2025-11-28 10:58:10)

  • TR62
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Re: Ubuntu + UFX + Reaper

I would be surprised if the hardware is the reason - the machine is a Asus X99 with Xeon 8core @3.4GHz USB3 ports, and SSDs. 
Plus I have it working brilliantly with Win10Pro at 64samples 48kHz with both ADAT ports in operation, thanks to the RME Windows driver, which I keep up to date.

It's dual boot.  Win10Pro and Ubuntu25.10, so we are comparing apples with (cooking) apples.

I am nervous Pipewire simply sits above ALSA - but if others are getting better results by setting aside PulseAudio, as Ubuntu Studio seems to, then it's worth a go.  I like the "zero copy" mentality in Pipewire's ethos.  It means time is not wasted needlessly copying buffers - the bane of driver ISRs - unless they are software modified by a node.

My experience is perhaps different, but I have found little tweaks do make a difference to ridding systems of audio glitches, and boosting performance - a good example is thread priority in DSP processes and DAWs - at normal priority, they get needlessly interrupted.  I have also found it pays to be super-precise about mods, and keep a log of the things I have tried, even if they were not successful.

I am reluctant to upgrade to a UFX III on the promise Linux will be better, although 22x22 becomes 94x94 which would give me more bandwidth - but what's the point, when the buffer size - and VST response, therefore, which is the reason I need smaller buffers - cannot be shown to improve?

Re upgrades, certainly in an ideal world, as the X99 is showing its age, but it's perfectly stable as a DAW system with Win10Pro, and unlike Microsoft: if it ain't broke... well, best not fix it. 

I probably would have upgraded the CPU to be fair, but Intel dropped the ball on their chips if you remember, the 14k series had issues.  And now that these chips are suddenly all AI AI AI AI AI AI oh, and some CPU cores you can use for what you want to do, I have lost interest.  AMD's 16 and 32 core offerings seem more suited.  But then, for a DAW, I need a platform, not a shifting sand.  The landscape is not as clear as it once was, to me at least.  YMMD.

5 Reply by Hopslost (edited by Hopslost 2025-11-28 17:17:28)

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Re: Ubuntu + UFX + Reaper

then, maybe Firewire is the way to go. Can't promise anything but with 20,- or so for a pcie adapter is worth a shot. Or you try a dedicated PCIe USB-Controller.

A hardware upgrade wouldn't need to be the newest at all. A 4 year old entry-level i3-12100 is already as powerful as the Xeon and twice as fast in single core performance. You'll get that together with a simple mainboard for less than 150, and in any case, save power.

Or you could boot a linux live system on someones PC too see if hardware makes a notable difference.

UCX II, BBF Pro FS, Quadmic II, PCIe HDSPe Multiface II, AIO Pro
  • TR62
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Re: Ubuntu + UFX + Reaper

Thanks @Hopslost,

Some really good ideas there with cheap hardware. Never thought to test i3.

The studio PCs were i7-6900K at one point, then I took one up to an 18core Xeon for coding work (eBay is a mine if you know what you are shopping for s/h), but as you rightly point out, the base clocks are low on Xeons - which is a crying shame, since they are extremely reliable, and predictable beasts.  Those i7-6900Ks were more like thoroughbred horses - twitchy, fast, and hungry - and in the end, all 3x succumbed to thermal/voltage spike death, despite surge protection.  The Xeons trundle on, just too slowly for pro-audio (ProToolsHDX notwithstanding - they work perfectly for that system too.)

My upgrade choice will probably be some flavour of 16core AMD, with >5GHz single core boost rate.

  • TR62
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Re: Ubuntu + UFX + Reaper

@Hopslost,

I used to run FW800 back when I had a Fireface800, but with USB2 settling so well, I retired the old Lacie FW card to the store.  It's in there somewhere.  Could probably do with a new one, offering more than older PCI-E speed.  Again, did not think to try FW instead of USB.  Thanks.

8 Reply by lunardigs (edited by lunardigs 2026-03-21 16:31:02)

  • Registered: 2017-11-18
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Re: Ubuntu + UFX + Reaper

Just a note here; USB 2 HID polling rate will impact the performance of a USB audio interface. Concerning USB 3, this shouldn't be the case, but if a device is running as USB 2 on a USB 3 hardware port, the same issue could emerge.

The gist is that you might want to experiment with lowering your USB mouse/HID polling rate, as higher rates can interfere with USB audio streaming and thus, force you to raise your buffer size.

Here's a decent write-up on how to experiment with it:
https://elamperti.github.io/dotfiles/mouse-polling.html