The L2T I had after 5 years starting exhibiting similar "sizzling/distortion", identical sounding to the mp3 that TheWolf2103 posted back in 2014. With both channel inputs/balanced/unbalanced/different instruments (guitar/bass/kybds)/different cables same symptoms. As someone mentioned, might be some Analog-Digital converter issue? Would love to hear how anyone else resolved (looking for a repair facility).
Thx, kirkjc1