When buying an amp made for US current 120V 60Hz as step down transformer will make it usable with the 240v we have in Europe. But we also have 50hz, does it matter in any way what Hz an amp is designed for? Will amp made for 60hz sound different if fed with 50Hz? Also would an amp made in Europe (50hz) sound sound different in the US than it was designed to sound? Thankfull for help..