Hi there Carsten

Thank you for your quick response. I did this and this is what I got with and without test tone:

Edit: I mixed up the channels by crossing the cables. The right channel is the louder one and without static noise on the second screen shot. But this should make no difference to understand the problem. The difference is pretty exactly 6dB which is very well noticeable.

You may want this information, too:

I switched the cables for this screenshot so these are the actual values for each channel.

Good. Then now methodically test all the available Input and Output Ref Levels from the settings dialog. You claim the breakout cable is new, so I don't expect two of these cables to have the same issue. But if one of the level switches of input or output is not working as expected it would show as your numbers do. But then there will be states where it works correctly, unless either input or output itself are broken.

Ref levels are usually in the hdsp setting app. See if there a setting where levels are equal.

I can clearly see 'Level' written two times in that dialog.

Set the input level to LoGain. Change the Output Level  betwen all three choices. Do any of these settings make the channels show identical levels on input level meters?

Set the output level to -10 dBV. Change the Input Level between all three choices. Do any of these settings make the channels show identical levels on input level meters?

If any combination shows one channel at lower volume then either input or output are defective. That again can be easily tested by using output L and plug it into L, then R.

That's it? No more replies?

So apparently the output is defective. Most likely bad QC. Can't say for sure since I have never used the analog outputs before. Can RME fix this? How much will this be?

Thank you vinark, your input is very appreciated. And yes, I knew you're not from RME. But Carsten is.

I thought myself about getting a DAC with S/PDIF input and balanced XLR outputs, but I haven't found something that's affordable by now. The point is that there's some noise on the headphones which I can describe best as some sort of sizzling. This is also occuring on the left XLR output, but not on the right.
I'm sure the result is the same with the unbalanced outbreak cable, but I will try this out to be sure. I need to get the box out of the cellar first, however.
It's a shame I didn't check on the analog outputs when the card was new. I'm pretty sure this is an out-of-factory issue.

Hi Daniel,

Sorry for the delay, I wasn't home so I couldn't look into this until today.

I just got the Cinch-Breakout-Cable from the cellar (thanks for suggesting this @vinark) and attached it to the HDSPe AIO, using a Cinch-to-Mini Jack connected to a Tascam DR-100MkII and it looks like the signal is equally loud. So what does this say? Did your distribution partner "Music Network" sell me a flawed cable or is there still the possibility that something is defective with the HDSPe AIO itself? The cable wasn't exactly cheap so I am not really eager to spend money on another one just to find out it doesn't solve the problem.

Cinch

XLR

So if it's the amp, can it be fixed? And again: How much will it cost?

Sure it can be fixed. Costs I can't comment, you have to ask at your local service center.