Try switching tubes, cables, channels on your source to isolate the problem.
for the past 2 days ive noticed this really high pitched whiny noise coming out of the right channel. audible without music. with music i just know its there because the music doesnt have any notes that high. if i unplug the headphones and plug them back in, it goes away for like a minute but then comes back again. using 421a and amperex 12au7 (bugle boy). any thoughts?
Also, take your set up into a distant room and try it there. It could be airborne digital or something that's leaking into your grounds on that household circuit( a different house would be definitive).