crackling sound out of right speaker

I am hearing a crackling noise coming from my right speaker.
I have done the following:
Swapped cables (from nordost to MIT)
Swapped left & right sides (left to right and right to left)
Swapped tubes in the amp
Still I have the same crackling sound when no music is playing on any inputs.
My system is:
B&W 802D
Nordost blue heaven speaker cables (all nordost interconnects)
VTL 2.5 preamp
Sonic Frontiers SFS 50
Any thoughts?