Roku model 4630X serial 7ka684863909. No external audio (except for testing). Crackling occurs both through on board TV speakers (Sony LCD about 5 years old) and remote speakers, with cords removed and installed. New HDMI cable had no effect.
Crackling/popping started on YouTube (SNL Eddie Murphy episode!). Crackles and pops we're always in the same place.
Other apps were fine. Then started to crackle randomly on Hulu. Netflix and Amazon soon after (crackling not in same place in playback).
Nothing worked: tried new HDMI cords, remote speakers, always crackled.
Yesterday, I read about volume leveling. It was on, I turned it off during playback, and now all apps work great, no popping.