What can shock you in an unplugged electronic device?
As long as the stereo is unplugged from the AC mains, it is mostly the capacitors that you have to worry about.

There are a few less common sources of unexpected voltage that are easy to disconnect:

An antenna going to the roof could get hit by lightning.

The Cable TV connection sometimes has an AC or DC voltage on either the shield or the center conductor, much higher than seems reasonable. The shield is supposed to be properly grounded at the entry to the building, but sometimes it is not. It can be a big surprise! The center conductor sometimes has DC on it for power.