MOTU UltraLite-mk5 and Linux on Raspberry Pi 4: noise on unused channels

Roon Core Machine

Synology DS418play

Networking Gear & Setup Details

Wired through UniFi switches

Connected Audio Devices

Raspberry Pi 4 running RoonBridge on Ubuntu 21.04
MOTU UltraLite-mk5 running at 192kHz connected to the RPi4 by USB

Library Size

How would I know?!

Description of Issue

This configuration works fine apart from the fact that any unused channels are filled with a loud static-like crackle. So if I configure the device channels in Roon as 2.0 then channels 3 - 10 are filled with noise. If I send 5.1 or 7.1 sound, those channels play back fine but the unused channels contain noise. If I configure it as 7.1 and send stereo, for example, as 7.1, then channels 3 - 8 are silent but 9 - 10 are still filled with static. And with 5.1 I get four channels of noise. If Roon could send 10 channels, I’m sure there’d be no noise at all!

There are no specific ALSA configuration setting on the RPi4. The UltraLite has no drivers installed under Ubuntu.

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Hi @John_Warden, I’m checking with the team on this. Thanks!

Hi @John_Warden,

I discussed this with our gear experts. Unfortunately, since this device isn’t Roon Tested, we don’t have this device in-house, and we haven’t heard any reports of similar issues with other devices, so we think this might be something specific to the MOTU.

We looked around a bit and found some discussion about this here:

We think reaching out to the manufacturer is likely the best place to start here.

Hi @dylan Thanks for the reply. Can I ask you to consider this a bit more closely. There are some other things that point to this beings something to do with Roon’s interaction with this 10 channel device through ALSA.

The reason I say that is that if I run the stream through an ALSA loopback device, into CamillaDSP and then out to the MOTU UltraLite this problem disappears entirely. That suggests that ALSA and the device have no problem dealing with each other. I’m also sure that MOTU would interpret this as confirming that the issue doesn’t lie with them.

Is there any further data I can provide? I’m a novice on Linux but I can run any test or debug that you’d like me to if you give me detailed instructions.

Are there other multichannel devices with more than 8 channels that Roon works with successfully through Linux? Can you give me some examples? Thanks

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If I purchased a unit to send in, does that help anything? OR does it really require Motu to do such a thing which I doubt would interest them as I’m sure Roon charges for that.

Roon Core Machine

Roon Rock NUC, Or Win10’s 10 PC running Roon server

Networking Gear & Setup Details

Netgear Orbi.

Connected Audio Devices

Raspberry Pi 4 running RoonBridge on Ubuntu-21.0
MOTU UltraLite-mk5 running via USB to RPI4, no fixed sampling rate

Description of Issue

I have the same issue. Noise on unmuted channels 9-10… Its seems Roon is feeding this channel noise.

Channel 1-8 work perfectly, no issues.

I tried using Roon’s mix to “show all” channels and route left and right to Motu outputs 9 and 10.
However noise is still present, and then nothing plays at all. This occurs using Win10 or a Linux Endpoint.

Its worth noting, channel 9-10 are free of noise using Win10/Motu Asio driver.

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This is my observation also.
No issue outside of Roon, or within Roon when I use Motu’s Win10 Asio driver.

Its my understanding Roon only addresses up to 8 channels? Is this correct?
Could the issue lie in the fact that Roon is only capable of addressing 8 channels, and subsequently for some reason (Kernel related?) sends noise to additional channels (9-10) in Linux?

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@dylan will Roon be actioning anything?

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My new observations running Ubuntu 21.04 server, with Roon server installed.

I appreciate the update, @grizaudio. Unfortunately, since we don’t have this device in-house, we are not able to test this on our side. If this is something we could reproduce with other devices or were hearing other reports of on other devices we’d be able to test this, but for now the best option is to continue to work with the manufacturer on this.

Hi @dylan,

Thanks for the reply.
As the use case is not the norm (I.e. Mutli-channel crossover), I suspect this could be a dead end. :frowning_face: But I understand, without a device its difficult. I would be happy to provide logs?

With Roon only addressing up to a maximum of 8 channels of audio, and Rock using quite an old Kernel, it seems as though Roon/Rock is somehow assigning noise/unwanted signal to channel counts above 8.

Point of note:
If I use Ubuntu 21.04, the noise is not present with my Motu directly connected to the Ubuntu/Roon Server. This seems to demonstrate a Kernel issue, which also suggests this is not an interface issue.

My trade off is Roon reports a processing speed hit between Roon Rock and Ubuntu/Roon server.

For those that are using the Motu MK5 with Linux, I can confirm no noise/signal on channels 9-10 when running Ubuntu 21.10 beta. Works perfect with a direct USB connection to Ubuntu/Roon Server core.
Kernel: 5.13.0-16-generic

Ubuntu 21.10

KERNEL: 5.13.0-1008-raspi

I guess Kernel 5.13 will come to RoPieee soon then

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