Blue Train SACD hum noise?

I just received the AP SACD of Blue Train. Sounds great. The cymbals sound so lifelike and natural -- a big improvement over the old Ron McMaster mastering.

After listening closely on headphones, I have a couple of questions:

1.) There is an audible "hum" on tracks 1-5. It's not terribly loud but you can hear it if you wear headphones and listen to the opening seconds of each of the first 5 performances. The best way to describe the hum is that it sounds like a vintage tube guitar amplifier. Is this hum on the original recording? The hum is not present on the 2 bonus tracks.

2.) The alternate take of "Blue Train" (track 6) has the left channel panned to the center. The appears to have been done in mastering? Just curious why this alternate take (track 6) was panned to the center on the alternate, since the horn / piano channel on the master take was panned hard left on the master take (track 1) on the disc.

I should note the above refers to the redbook layer of the new AP disc. Is anyone else hearing this hum? I'm guessing it's on the master tape? However the hum noise also surfaces between the songs, where tape leader should occur? If so, that would suggest the hum came from the mastering board? Also, the hum is not present on the bonus tracks which were mastered at a later time?

 

I tried to hear this but through my speakers, and at the volume that I listened at, I could not discern this.