Maybe a touch of flat black paint or felt pen might help?
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Yes a black sharpie has worked well for me in the past. It will dim it in increments as you put in on in layers.
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So I’m unable to get the Matrix to work for me with Mac or Lumin. I have the 9v iFi iPower X plugged into it and the LED up front is not on. I see red lights inside the Optical input so I know its getting power. Am I supposed to turn on any of the DIP switches on the bottom of the Matrix? Or did I just get a bad unit?
So I just discovered something interesting trying to get the Matrix to work with my MacBook Pro. Although the Audio MIDI does not see the Matrix as an output device, if I go into System Information and check the USB, it shows up as “X-SPDIF-2” being connected to the USB. The computer is not recognizing the Matrix as an audio output device. I have a message into Matrix to see if there is a driver that I need to install. Will let you know when I hear back.
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There are no drivers needed for Mac OS only Windows.
If the front light is not lit up according to the manual it means that the Matrix is not seeing the USB from the output device. Since it is two different devices you might want to try a simple certified cable like from a printer or at least another cable. If there was a cheap cable in the Lumin box try it.
My assumption was if powered on by external power and it lit Green. Either way I do get a Green light when I plug in a USB. I’ve used the USB that came with the Matrix, a Nordost, and a Curious and neither change the issue. I see the Green light in I2S on the DSD but no Audio. I’ve emailed Moon Audio who I got the unit from hoping they can replace it or give me my money back.
Went through some troubleshooting today with Moon Audio and the Matrix is still not working with the Lumin and DSD. They had me turn all of the switches to the on position and had me test the AES/EBU and Coaxial outputs and still nothing. The DSD shows a green light for each connection just no music. Very Weird.
Sorry I’m replying rather late to this thread but hoping someone may have experimented with voltage and discovered the “sweet spot” for powering the Matrix - X SPIDF 2 with the Uptone LPS-2 power supply. What’s the consensus, guys? Does the DSD SQ improve going from 5V to 7V, from 7V to 9V? I presently have it set to 9V to power the Matrix and it definitely renders a different sound than did my ifi 5. Replies appreciated. 
I strongly prefer the sound of 9 volts powering my Matrix. 7 volts washes out for me. I don’t mind 5 volts though. I keep mine at 9 volts, it runs at a cool temp and all of the bad things people worry about have not happened to me.
Let your ears decide.
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9 volts all the way for best sound quality, problem is some people disagree 
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So I got the Farad in hoping it would make the Matrix work with the Lumin and DSD. But it’s a no go. Now I’m forced to send back the unit to Moon Audio so they can test and see what is wrong with it.
Is it possible I’m not setting it up properly in the Roon settings? Does anyone use Roon and these products and can tell me what I could be missing? Thanks.
I have the same setup as you and also use Roon. Never had any issues. Sorry to hear about your problems. Sounds a lot like a bad unit. But to ensure: this is how my „Device setup“ appears in Roon.
I then „mask“ the Matrix as the following DSD, but just for aesthetics:
Can you share a screenshot of that setup screen? And maybe also a screenshot of the Roon signal path?
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The upsampling to 32 bit could be the issue. (If that is passed on to the DSD silence will be the result. Only max 24 bit will work).
Either choose the DSD in Roon to „mask“ the Matrix (click „Not your device“ and then choose PS Audio → DSD) or manually correct it.
Also: have you enabled any upsampling in the LUMIN settings?
I’ve gone into the Lumin and made sure MQA was off since the Matrix doesn’t support it. Here are the Sample Rate Conversion settings.
The last screenshots confuse me: the LUMIN now has the DSD icon (top left)? How did you do that?
I would start with trying to get a clean (lossless) signal path first:
Disable DSP in Roon. Set up the Matrix as DSD. Disable anything in LUMIN besides Roon Ready.
It then should look like this:
Yep even changed all of the settings in Lumin App as well as the 24 bit in Roon that you mentioned. Still no audio. I appreciate the help but I’m pretty sure its busted and needs replacing.
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Have you try just using just the Lumin app and take roon out of the picture? I’ve heard others having problems with roon not recognizing the Matrix.