I have a JVM215C(2017),on gigs I hear sometimes a double or ghost note on single notes,but not all the time. I've blamed the speaker because when I use it with my Mesa EV cab(without the combo speaker)I don't hear this effect. But I was watching a Y/T demo of the Blug Amp1 & in the dem Thomas matched up his Amp to a Marshall Head & 4x12" & the Marshall made the same or similar double note sound that I hear in my Amp,Thomas commented on it & seemed to say it was a side effect caused by mains frequencies?. I have no idea what this means ,so I thought i'd ask on the forum,is this a known CURABLE issue or should I still suspect the speaker. Thanks for reading.