How I "safely" use 2-prong amps until I change to 3-prong!

[Wilder Amplification]

-master wankeryourselfer-

Wouldn't that be a "master baiter"?

[Dave Curtis, dB AudioTech]

Please note that I'm familiar with the code used in the USA (the NEC).

Hi Steve. The way I see it is that although the Neutral and (Protective) Earth seem to be redundant, being both connected someway to the distribution transformer center tap, in fact they are not the same.
The Neutral always carries the full return current

It carries the unbalanced current. That's why it can be the same size as both ungrounded conductors (assuming 120/240 single-phase service)

from all loads fed by that transformer, probably hundreds of amperes, and is a long wire to boot, maybe 100 or 200 meters for the furthest users, even more for sparsely populated suburban or even rural area. That means it often is quite a few volts away fron real ground potential.

The NEC requires fairly subtantial earthing (real ground) at the service to help aleviate that. That said, it's common to measure a few volts from ground to neutral occasionally on branch circuits, depending on what's running in the house.

On the other side, Protective Earth wire normally only carries relatively minuscule "loss" (not perfect insulation) currents and only when some appliance chassis becomes live, the 10 to 15A allowed by its protective fuse for the second it takes to blow, a very different job.

It's only purpose is to direct fault currents to ground, and is sized according to the overcurrent device.