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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.

Post Subject: Daisy chaining of ground wiresPosted by JOHNR on: 11/23/2015

You should take care that you do not daisy chain the ground leads. Refer to following text.

From my perspective, you should treat the L and N leads as one type of circuit and the PE as a separate circuit. Electrical codes, rules etc do not insist that the PE is always carried along with the L+N.
Very often amplifier builders are sloppy as to how the PE is connected. Sometimes the PE is used as a part of the audio return path to for example, a line amplifier. To get around the hum that will result, they use a ground lifter device eg 10 ohm resistor even a pair of diodes back to back.

A point to note is that line and neutral generate noise of one type whilst a PE should not be carrying noise at all unless you use one of the clever high cost power cords.

A system that can work well is to create a single node or terminal where all ground leads are terminated. This terminal is then connected in turn to the electrical panel.

Noise can come down any wire but cannot go back up any other wire so there cannot be any passing of noise from one piece of apparatus to any other.

The choice of wire to be used is important since stranded wire has much higher inductance than a single core. This is important since one can inadvertently create a high frequency TANK circuit.
Thus, this central ground terminal should be connected using the thickest single core wire that is available. Here, in a metric cable environment, single cores are not available. Tip - go and look for plenum rated fire system cabling supplies. Generally XLPE insulation which is better anyway than standard PVC type BUT costly.

On an earlier posting, i recommended using USA cooker cable since this cable is unusual in that all of the 3 conductors are the same size. Generally electrical codes require the ground conductor to be 1/3 to 1/2 of the line conductor size. In effect you obtain a double sized ground path which is useful to have.

If you wish to check out ground currents etc, purchase, hire, beg, borrow or steal a clamp on "Hall effect" ac/dc meter. This will tell you that line and neural are correctly balanced and if there is any current in the ground path.

regards
John

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