stereo_buff wrote:Who cares? TweakyDude audiophiles sure don't, and I doubt they would pay much attention to the safety advice, even when true. The unit power supply, by design, does not utilize a ground and improper grounding will cause common-mode problems. Bob P can ground his unit and anyone else can 'take their life in their hands' if they so desire, at their choice. In the USA, the low side of the line is connected to ground at the panel, so barring strange occurrences, one side of the power line is effectively at ground (or some other very low potential) anyway.
I do have a technical background.
People who don't understand the problem don't have reason to care.
People who do understand the problem have good reason to care.
I don't doubt that TweakyDude audiophiles don't care. If this thread demonstrates anything, it demonstrates that audiophiles could stand to learn a bit more about electrical safety.
The advice that you gave about the low side being connected to ground at the panel isn't going to protect anyone when an internal malfunction causes an amp chassis to go hot, and that's the exact condition that's addressed by the safety standards that require chassis grounding on a Class I appliance.
Don't go relying upon the fact that neutral is connected to ground at the service panel to protect you. That connection won't do anything to help you in an amp design like this one if the chassis goes hot. Because neutral is connected to a transformer and not to the chassis, there is no neutral-to-chassis connection inside of the amp. The neutral-to-ground connection at the service panel cannot prevent your electrocution should the chassis go hot because there is no connection between the chassis and neutral. (As a parenthetical comment: A neutral to chassis connection inside of the amp is a really bad idea -- all that you would need to do is to reverse the polarity on the plug and you'd get a hot chassis!)
The whole purpose of the ground wire is to prevent a hot chassis from ever occurring, which would present an imminent risk of electrocution. Let's consider the two possibilities:
No Ground Wire and Hot Chassis: Chassis remains at an elevated potential of 120VAC, ready to shock you when you touch it, or any gear that's hooked up to it. There is no low-impedance path to ground, so the hot chassis remains hot. You're at risk of being electrocuted if you touch the chassis.
Ground Wire and Hot Chassis: Ground wire on chassis provides an immediate low impedance path to ground, causing the device's fuse to blow as soon as the chassis goes hot, turning off power to the unit and removing the risk of electrocution.