Charles Hansen is right, anything with a smp power
supply can contaminate into the wiring of the house, and it's airborne efi as well.
Do an experiment, tune a portable AM radio down low on the dial around 700khz, so there's no music and it's not muted, just static, then go near to a smp power supply or class D amp and you will hear what rubbish rf rubbish emits from the speaker of the am radio.
I had a smp wall wart pugged into the power of my house, I was driving up to my house and the radio in my car started squeal, the closer I got to my driveway the worse it got, I pulled up next to the room it was in and it was really squealing bad. I pulled the smp wall wart from the mains and the noise from my car radio stopped.
It was using the whole houses wiring as a transmitting antenna for it's rf rubbish to contaminate anything close by.
I say ban all smp's and Class D amps.