So the story starts from me picking up my headphone to listen to a single singing playing track on the spur of the moment.
I assumed a mono like centered image. But no, the acoustic image was leftward. That's odd.
I started to worry of something wrong in my sound reproduction system. I listen to another song which happened to be Miyuki Nakajima's "Truck ni Nosete", also leftward vocal imaging song. That really scared me.
First I tried wearing headphone left to the right to make sure it wasn't my hearing issue. Yeah, it wasn't. Acoustic image moved to the right as I expected.
Then I tried to replug headphone, switch to another headphone. Still leftward image.
Then I tried to restart my computer and audio interface. Didn't change a bit.
While I was giving up my hope and planning a warranty repair, software volume unit meter was checked subconsciously. The signal level at left channel was continuously higher.
Knowing it wasn't a hardware problem, I listened to another song in which image drifting problem wasn't found. No software problem as well.
But why would some audio mixers not placing vocal image in the center? Anyone got an idea?