Cheap power supplies...

[Chromatischism]

I got a new LED lamp and heard a high-pitched whine coming from the power supply. I got out the phone and sure enough:

I'm not sure what it takes to design a quiet power brick, but this isn't doing it for me.

 

[Katji]

We need.../"there needs to be"/ some tested alternatives to those iFi products. I once saw a list - some sort of tests - of phone chargers, including Apple and Samsung, and fakes or cheaper alternatives, but it didn't include noise testing. - Or the voltages we'd probably need for audio gear.