10.10.4 - Output stream 0-1 won't play to headphones

[CervantesX]

Hey y'all. So:

 

Yosemite 10.10.4 on an Asus p5q pro built in sound.

Known good headphones (x2).
I plug my headphones in, I get sound out of 1 side only.

Plug them in to my ipod, it's fine.

The sound balance is in the middle (on every output device)

In the MIDI control panel, volume is up on each channel.

Format is 2 channel 24 bit, 192k hhz.

 

Now, here's where it gets fun. If I go into MIDI/Headphones/Configure Speakers (stereo), channel 1 is left and 2 is right. I get sound out of the right earbud. If I swap the channels around so 1 is right and 2 is left, i get sound out of the left earbud. So I think we're OK to say this isn't a hardware error.

 

So, what the heck? How is my one output stream muted, and how can I fix it?

 

Worth noting, I've been through these panels a few times because I was trying to get 5.1 surround sound working. I haven't made any kext/config file changes, but I have been banging around in the control panel a bit making an aggregate device (since deleted). Also worth noting, this used to work. I don't remember when it died, but I remember it working up until a while ago.

 

Any ideas?