Once a while, it's nice to listen to music a bit louder than usual. I finally found pretty good & not too pricey setup. Sony MDR7506 headphones (98$), Douk Audio U3 Mini Class A Headphone Amplifier (42$) and SoulBay 48W Universal AC Adapter DC (19$). While there is some minor (not very loud) frequency pushing through when no music is played, it gets lost once the music is on (hard to know what's the source - amplifier, ACDC adapter, Florida electricity or iPhone 🤷🏼♂️ - but the headphones sound pretty good and quite loud as well without the amplifier directly on iPhone and without the "frequency"). Over all with amplifier - not perfect, but good enough. On brighter side, these are definitely going to be by far my favorite headphones... (and yes - with amplifier it does get REAL loud) Loud & clear Mini setup with iPhone Update 01/20/2022: Seems like ACDC adapter was the weakest link causing the "frequency" noise. If you use provided USB cabl