You are correct, in previous posts, the OP had indicated that he had Chassis, house ground and HV middle wire bolted together, but for some reason lifted his signal ground from it.
The 10R suggestion was a safety, should some HV leak into his signal ground (and therefore to his guitar) he would get a shock, the 10R would have protected him.
It is all academic now, he has connected all together.
Yes, the Dot stuff is wrong. The chassis must connect directly to mains ground (wherever possible).cnpope said:
If a resistor is used to separate signal ground from the chassis then it must be a very fat resistor - fat enough to survive being placed across the mains for long enough to blow the fuse or trip the breaker. This probably means either or both of ELCB at the distribution box (not a fat fuse) and (in the UK at least) a suitably low rated fuse in the plug. 10R means 24A (in the UK) which should blow a 3A fast-blow fuse within a few seconds; until then the resistor is dissipating 5.8kW!
Assumptions, assumptions !
Chassis is connected to house ground , we have already established that.
Signal ground (if lifted) may have a few hundred volts of HV leakage, from a transformer that can supply milliamps before it goes open circuit, and it should have a fuse of few milliamps for the HV too.
Little Dot is actually correct, sometimes you get a ground loop between a poweramp and a preamp, this is one of the ways to combat it.
some people lift the house ground altogether, NOT SAFE, the 10R resistor is much safer.
Don't just get your calculators out and measure ohms law and come up with unrealistic figures.
This is DIY audio, we deal real life situations, mains live wire does not get bolted ACCIDENTALLY to a signal ground.
Kiloamps, kilowatts . . . goodness me.
The assumption I make, which is the correct assumption, is that the equipment will remain safe (or at least rapidly become safe) even if a mains lead breaks free and touches the chassis or a signal connection. A metal chassis must always be grounded to the mains supply. No lifters or breakers of any description. Then the signal ground should, whenever possible, be connected directly to the safety ground too. If not possible, due to hum problems, the signal ground should be connected to safety ground in a way which can pass a large fault current. A small resistor won't do.
I hope you live alone, and are not subjecting your family to potentially dangerous DIY equipment.
I hope you live alone, and are not subjecting your family to potentially dangerous DIY equipment.
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