Grounding Question

@atmasphere  can you elaborate on your last statement bout two pronged older equipment? I have an amp when you turn it on you get a ground loop hum hd it goes away when the preamp fully turns on. 

Thank You @erik_squires!
Finally, someone with a little snippet of Electronics Knowledge.
You just brought up one of my Pet Peeves. Just about every one of the Commerciale Power dist. box manufacturers will try to convince you that they can carry sufficient current for your equipment and yet they almost all exclusively use just a tiny copper trace on a circuit board to deliver all of the power.
On another point I agree that you should NEVER depend on your inner connects to carry the ground. Though most of the time the transients that they do carry can safely handle, it is definitely insufficient to carry a serious load. BUT Most equipment that doesn't haver a dedicated ground wire/pin do utilize the Neutral side of the power cord as a pseudo ground. There is lots of debate over how much is enough or too much grounding. You can go too far and actually create ground loops which will actually DESTROY your sound.

Modern electric devices without a ground prong on the plug are double insulated. They're constructed in such a way that they're safe without one. Audio aside, this is my preference for any power tool.

BUT Most equipment that doesn’t haver a dedicated ground wire/pin do utilize the Neutral side of the power cord as a pseudo ground.

@esarhaddon 

Not true now. Today if you have double insulated equipment there’s no legal/safety need to have an AC ground. The neutral and signal grounds in those pieces of gear have NO relationship.

This USED to be true with older gear and appliances like dryers, etc, however even those appliances now must be 4 prongs. My quite modern (electrically) sub has 2 prongs, but a wooden case so no chance for a short to the chassis.

 can you elaborate on your last statement bout two pronged older equipment? I have an amp when you turn it on you get a ground loop hum hd it goes away when the preamp fully turns on. 

@dinov That doesn't sound like a ground loop at all.

Normally the procedure for turning on any audio system is to power up the preamp (or in pro audio systems, the mixer) first. After it has stabilized then you power up the amplifier. In this way you avoid buzzes, thumps and the like as the preamp turns on.

When the preamp is off, it can act like an antenna for buzz and hum. When its turned on, its a much lower impedance so the antenna thing goes away.