So, I get a weird “buzzy” or “fuzzy” feeling when using things connected to a USB charger, unless they’re good quality grounded devices.
And yes, this includes Apple’s devices, until I use the “extension cable” which is a three-prong grounded cable.
There’s a small difference on those Apple cables - inside the “mating” connector are ground tabs which connect to the “lug” on the power brick. It’s a little hard to see, but if you squint you can tell the difference.
| Grounded | Un-grounded |
|---|---|
 |  |
The term for what causes it is a “floating” ground, because the device doesn’t have a “true” ground.