Well, I figured out how to change the tubes. The Allnic comes with a special tube puller. That did the job. Didn't notice much of a change changing tubes but an hour later I noticed a hum. I played with cables going from balanced to single ended and now I have a permanent hum - a loud permanent hum. Doesn't matter what I do. Checked AC cable, tried different sources, different cables but the hum remains.
Looks like I have a broken Allnic :(
Looks like I have a broken Allnic :(