Yesterday I had a show with a monitor mixer and a FOH mixer, where the hardwired split happened via Y cables before the snake. Kind of a crappy provider who had 2 decent mixers but pretty much everything else was cheap chinese equipment (knockoff JBL SR speakers powered by knockoff Crest amps).
Phantom was supplied initially by the monitor board only, (later tried from both boards at the same time, not that it did anything to help) for the few condensors (was using my own mics) that required it on stage. Pretty soon we were faced with huge amounts of phantom popping that came and went even when nobody was touching anything on stage. It didn't matter what channels in the board had phantom turned on, the problem still occurred if even one channel was on.
This wasn't an issue when phantom was turned off so the provider's only solution was to remove all condensors and replace with 57's and 58s. Not my ideal solution but we were out of time to fool around.
Question: If this was occurring regardless of which channel was supplying phantom, what could have been the issue? Something to do with the snake?