DIY Raspberry Pi HiFi

I’m asking here because some of the audiophile power supplies I’ve been “researching” on the net also appear in Raspberry Pi contexts. I’m hoping that someone who has a bit more DIY experience might shed some light on the perplexing hum I’ve experienced when I add charging to an iPad or iPhone while listening to my Audeze LCDi3 and then (gasp) touching them.

I’m trying to figure out if I should blow $50-$150 on a better USB charger…