[redmaw]

Hi,
 
I have this issue where if I play a multi channel audio file the channels are not mixed correctly for a 2.0 setup when I use the optical (SPDIF) output. It sounds like I am just getting the FR and FL channels for the most part. I double checked the settings in the media player and everything I could think of was set correctly and if I switch to USB connection everything sounds fine. Anyone know what else I could check that could be causing the problem?
 
For those curious as to why this is a problem, my better DAC does not have USB input and my other DAC/AMP needs to be retired soon

 

[MindsMirror]

Well, it sounds like your software is not mixing properly or outputting the correct format. We can't be of much help without knowing any specifics about your setup. What are your source files, software, S/PDIF source, and DAC?

 

[redmaw]

The source file I was using was a mkv. The S/PDIF source is my computer (Win10) and the DACs are a Gungnir (first generation) and a Yulong DAH1 Mark II (the one with USB interface). The media player was MPC, but all I do to change from USB to optical is go to the options->playback->output->Audio Renderer and select the device. I poked around the system device settings but I'm not sure what to look for.

 

[MindsMirror]

In MPC, go to View > Options > Internal Filters > Audio decoder. In the mixing tab, set it up like this:
 

 
That should force the MPC audio decoder to downmix everything to stereo.

 

[redmaw]

Thanks MindsMirror, that pretty much fixed it. It sounds slightly different still but I rarely deal with multi-channel audio and when I do I'm not that picky about the quality

 

[MindsMirror]

The mixing levels might be different than you were hearing before, but the levels I showed should technically be correct. They are the levels recommended by Dolby for downmixing surround sound to stereo. It might also be quieter. The normalize matrix check box lowers the levels to ensure that even the loudest possible signal on all channels can never be clipping after mixing. You can select clipping protection instead of normalize matrix, I think that should prevent clipping by just reducing the volume as much as it needs to.

 

[redmaw]

It is a quite a bit quieter, but I would say the difference was that the audio via USB was more forward and had bit more bass. It could be because the mixing makes the levels of each channel are more uniform, which fits what you are talking about I think. I am still not sure as to why S/PDIF or USB would make a difference, I feel like the OS and application should be generating the same data to be transmitted. The only possible reason I can think of is that the DAC is doing the mixing to 2.0 itself and the driver advertises as multi-channel so it gets a different audio stream than the S/PDIF output is used.