Grounding Question

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.

erik, I'd bet that your sub has more to it than merely a wooden case. The electrical portion is likely isolated on plastic. Wood isn't a suitable insulator.