• From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Topic: KEXT Driver Not Found by OSX on Startup

I'm running a UFX3 with the kernel extension driver firmware 21 driver 3.39 as this is the lowest latency and I have found to be the most stable driver. My Mac is a Mac studio running recent versions of Tahoe.

The issue started 6 to 12 months ago only very occasionally. You would boot the Mac and everything looked like it had booted up perfectly but there was no audio communication between the computer and the interface. If the interface had live inputs from its last used state, they were still working so the interface was passing hardware inputs to hardware outputs. It just was not receiving any audio from the computer.

The adopted workaround has been to just go into the USB settings and toggle the sample rate and all of a sudden audio would start to pass again as expected. After communication is fixed, the system is 100% stable for hours or days at a time until the next time this cold boot issue occurs.

Initially it wasn't annoying enough to even report but in recent months the issue has become more prevalent possibly up to 40% of cold boots the problem occurs.

Any thoughts would be much appreciated.

PS: I also run a Mac mini M4 with UCX2 connected as a live keyboard rig with the same OS and driver versions and this system has not shown this problem.

Kind regards

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • From: Haimhausen
  • Registered: 2012-04-02
  • Posts: 435

Re: KEXT Driver Not Found by OSX on Startup

Is the UFX 3 seen in the system report of the mac under USB when it is not responding? Does replugging the USB cable help as well?

Regards,
Audio AG Support

Audio AG Support's Website

  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

Thanks for the thought and apologies for my slow reply but it has just happened again so I went into system information/USB and the UFX3 is seen in there while the no audio fault is present.

This time however it was a little different in that while the system was already running at 48khz and passing stereo audio as expected I switched to a new workspace that I have set up for Atmos mixing and monitoring in Totalmix and simply doing this caused the no audio issue to appear.

I didn't try to unplug/ plug the USB cable as it's deep in the back of a rack but the usual fix of switching the sample rate to 44.1 and back the 48Khz restored the audio.

Kind regards

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • waedi
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  • From: Swiss Zürich
  • Registered: 2020-12-08
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Re: KEXT Driver Not Found by OSX on Startup

And switching sample rate was done where ?
In the MacOS Audio-Midi-Setup ?
In the RME Settings ?

M1-GoldenGate, Madiface Pro, Digiface USB, Babyface silver and blue
  • From: Haimhausen
  • Registered: 2012-04-02
  • Posts: 435

Re: KEXT Driver Not Found by OSX on Startup

Changing the sample rate, kind of resets the USB Port as well. You could try a differnet USB port on the Mac and/or try a different USB cable.

Regards,
Audio AG Support

Audio AG Support's Website

  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

Waedi, sample rate switching was done in RME settings.

It only happens occasionally but strangely after the issue appeard yesterday for the first time in a month or more this morning the cold boot up showed the issue again.

I will get around to trying a different USB port and cable soon but I don't hold much hope in this improving things. The computer is a Mac Studio and the UFX3 has it's own dedicated USB 3 port with no other device attached on that port and the factory USB 3 cable is used and the UFX3 performed very well for the first year or more before the problem began. My instinct is it's some OS level issue that appeared after an update. Maybe it's time I went and gave the driver kit driver another go. I know I'm going to have to eventually.

The issue is not killing me and once the fix has been applied the whole system is very stable but I do appreciate the thoughts guys.

Kind regards
Paul Najar

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

7 Reply by waedi (edited by waedi 2026-10-01 01:29:00)

  • waedi
  • DAW Mastermind
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  • From: Swiss Zürich
  • Registered: 2020-12-08
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Re: KEXT Driver Not Found by OSX on Startup

paulnajar wrote:

Waedi, sample rate switching was done in RME settings.

Conclusion : The driver was up and working somehow or partially.
I would also try the DK and MacOS 27 (with a backup ready)

Totalmix is listed and enabled in the Microphone access in MacOS system preferences / Security & Privacy ?

M1-GoldenGate, Madiface Pro, Digiface USB, Babyface silver and blue
  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

waedi wrote:
paulnajar wrote:

Waedi, sample rate switching was done in RME settings.

Totalmix is listed and enabled in the Microphone access in MacOS system preferences / Security & Privacy ?

Well this could be a clue. I do a lot of live multichannel audio recording with the UFX3 amongst other things so microphone access works in some shape or form and my guess was it definitely must be listed in Microphone within privacy/ Security but it's not! Digicheck NG is but not Totalmix and I could see no way to add access.

The web suggested unlocking the section to add a new app but I can't see a way to do that. I think the Gemini AI was referencing an earlier MacOS version. I'm on Tahoe 26.7.1

I also started to wonder whether it is Toitalmix that requires microphone access or the RME KEXT driver extension. I looked in extensions in System Preferences and there is no mention of it there but when I gather System Information/ Extensions the RMEFirefaceUSB KEXT extension is listed.

Any thoughts Guys?

Kind regards

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • From: Germany
  • Registered: 2007-04-10
  • Posts: 11,208

Re: KEXT Driver Not Found by OSX on Startup

Does this ever happen if you switch on the UFX after bootup? Or does that sequence make a difference? Have you tried another cable?

Regards
Daniel Fuchs
RME

RME Support's Website

10 Reply by MC

  • MC
  • MC
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  • From: Germany/Thailand
  • Registered: 2007-04-06
  • Posts: 27,176

Re: KEXT Driver Not Found by OSX on Startup

paulnajar wrote:
waedi wrote:

Totalmix is listed and enabled in the Microphone access in MacOS system preferences / Security & Privacy ?

Well this could be a clue. I do a lot of live multichannel audio recording with the UFX3 amongst other things so microphone access works in some shape or form and my guess was it definitely must be listed in Microphone within privacy/ Security but it's not! Digicheck NG is but not Totalmix and I could see no way to add access.

TM FX does not require mic access unless you use a Babyface (FX record channels). I explained that to waedi already before.

Regards
Matthias Carstens
RME

MC's Website

11 Reply by waedi (edited by waedi 2026-10-01 16:57:36)

  • waedi
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Re: KEXT Driver Not Found by OSX on Startup

I thought the UFX lll with all FX suited needs the access for FX record channels.

@Paulnajar : Yes, that was older MacOs where we could manually add applications to the microphone access.
Apple changed that and now a popup appears as soon a program with audio input channels tries to run.

What else can block the communication of the driver to the unit ?

USB-port, USB-cable, CC-mode

Is the unit set to USB-2 and CC-mode ?

the driver per se is not blocked, the Settings dialog does work.
But the audio from or to the unit is not open. (Typical symptom of mic access denied)

M1-GoldenGate, Madiface Pro, Digiface USB, Babyface silver and blue
  • From: Haimhausen
  • Registered: 2012-04-02
  • Posts: 435

Re: KEXT Driver Not Found by OSX on Startup

waedi wrote:

USB-port, USB-cable, CC-mode

Is the unit set to USB-2 and CC-mode ?

It cannot be CC-Mode or acces denied. Because the issue happens occasionly. Otherwise it would be continuesly not working.
USB-Port or cable is more likely. Because after a reset of the USB port (sample rate change) it works again.

Regards,
Audio AG Support

Audio AG Support's Website

13 Reply by waedi (edited by waedi 2026-10-03 05:31:48)

  • waedi
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  • From: Swiss Zürich
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Re: KEXT Driver Not Found by OSX on Startup

If you flip the interfaces, UCX ll vs UFX lll , does the issue also flip or stay with the computer ?

M1-GoldenGate, Madiface Pro, Digiface USB, Babyface silver and blue
  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

MC wrote:
paulnajar wrote:
waedi wrote:

Totalmix is listed and enabled in the Microphone access in MacOS system preferences / Security & Privacy ?

Well this could be a clue. I do a lot of live multichannel audio recording with the UFX3 amongst other things so microphone access works in some shape or form and my guess was it definitely must be listed in Microphone within privacy/ Security but it's not! Digicheck NG is but not Totalmix and I could see no way to add access.

TM FX does not require mic access unless you use a Babyface (FX record channels). I explained that to waedi already before.

Thanks for clarification MC.

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

RME Support wrote:

Does this ever happen if you switch on the UFX after bootup? Or does that sequence make a difference? Have you tried another cable?

I haven’t tried this power on after computer boot but I will.

Regarding your suggestion to change cable, I went looking for a new USB3 - USBC cable thinking I had one but best I could find was USB3 - USBA so I added one of my A to C adapters and in a few hours of just Atmos listening there were a few dropouts. Worse performance than the previous cable which pretty well never had dropouts under the same conditions.

So if I were to buy a new cable - USBc to USB3 is there one that comes highly recommended above others?

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

waedi wrote:

I thought the UFX lll with all FX suited needs the access for FX record channels.

@Paulnajar : Yes, that was older MacOs where we could manually add applications to the microphone access.
Apple changed that and now a popup appears as soon a program with audio input channels tries to run.

What else can block the communication of the driver to the unit ?

USB-port, USB-cable, CC-mode

Is the unit set to USB-2 and CC-mode ?

the driver per se is not blocked, the Settings dialog does work.
But the audio from or to the unit is not open. (Typical symptom of mic access denied)

Your logic seems good and yet…
UFX3 is in full bandwidth usb3 mode and no cc. I need it that way has I use the MADI port a lot. The computer port it’s connect is a usb3 3.1 port.

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

Also meant to mention that I have tried a different usb bus on the same computer but still got one audio loss event. Isolating the issue will require a new usb cable for sure. Wishing to buy the best most recommended model…

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website

  • From: Sydney Australia
  • Registered: 2007-06-09
  • Posts: 268

Re: KEXT Driver Not Found by OSX on Startup

Quick update.

I managed to get a new "Cable Matters" Brand cable from Amazon overnight and plugged it in, booted the Mac and the no audio issue appeared straight away. I've also purchased a Lindy cable but it will take few days to arrive and I'll test with that as well.

The next step I think will be to try a different USB bus on the computer.

__________________________
Paul Najar
Jaminajar Music Production
www.jaminajar.com

paulnajar's Website