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I recently purchased an Ultraligth mk5

Seems to work well, except for the headphones producing nothing but a mono signal.
I went through everything. Tried different headphones (still mono), put my headphones on a different interface (works well) , checked all possible configuration options, but de situation remains the same: speaker outputs give a stereo signal, headphones just mono.

I am using a Windows 11 PC and al input comes from the PC. There is no difference what the source on the PC is or how I configure the sound in the PC. I have virtual pipe organ that supports multiple channel output and is using the ASIO driver. All well except for the phones, the same when I just play some Youtube (stereo test!) content).

Interface has the last firmware.

Any thoughts? Thanks in advance!

If everything you monitor is coming from the PC, that—your DAW—is where you set the mix. I suspect that you have everything outputting to a Mono bus. Make sure your output is to a stereo bus. This is normally the first problem I have to solve for any of my users. If using Digital Performer, many of us could post some screen shots. That's not the only possibility, however.

You may have set up a Mono monitor mix in your Ultralite. Read the manual for your many monitoring options including Output, blending the Input and Output etc. You can create a separate stereo monitor mix for each pair of outputs if you desire(!). I see that this manual was updated 2/23 so it may be newer than the one that came with your unit.

https://cdn-data.motu.com/manuals/usb-c ... _Guide.pdf

The Quick Start page has a pair video tutorials for getting started, one each for Mac and Windows.
https://motu.com/en-us/products/gen5/ul ... g-started/