Subwoofer NOT working with Stereo sources playback! Denon X3400H
Hey all - I have a Windows 10 (latest version) HTPC with a Nvidia gtx1050 going to my denon avr-X3400H receiver via HDMI. Pretty standard setup.
I have all movie audio pass through to the amp (Dolby, DTS etc), and it works perfectly. Amp switches over and plays perfectly, subwoofer and all.
I have Windows 10 configured for 7.1 output, and when I test all the speakers in the windows sound panel, they all work - including the sub.
Now, when I play a stereo source, whether it is an mp3 in winamp, or a stereo tv show in MPC or VLC, it ONLY plays from the front two speakers, and no subwoofer. Even though the amp shows "M in 7.1"
I have found a workaround for the mp3 with foobar2000 player, which upmixes stereo to 7.1, then all the speakers are in play and work fine.
I have tried fiddling with the 'mixer' option in MPC-HC, but it simply didn't so anything when I selected 5.1 or 7.1 for the output. Just played stereo, no sub.
Is there something easy I am missing?
I don't want to change any settings on my amp if it can be avoided, as most things I play are true surround sound.
Any ideas would be greatly appreciate, sorry for the TL;DR!