Cable directionality

seandtaylor99 - I have also tried it and found no difference in my particular system. I believe that the results are very system-dependent. In systems with poor grounding, it could make a big difference in theory.

BTW - I am also an EE with 26 years experience, and a cable company to boot!

In general, the reason that the shield of a twinaxial cable is grounded at the source is because this is where the signal is being driven. The most accurate ground reference for a driver will be at the driver, not at the destination component. If there is noise developed across the signal return, then this will not be induced on the shield as it will if you ground the shield at the destination end. The felling is that the ground will be noisier with respect to the signal at the destination end compared to the source end.

Bigtree - Here is why your single-wire scenerio worked: The return current for the signal was running through the ground of the power cords of the two components. This is simply batteries and bilbs. The current flowing in the signal wire must return on another wire. The optimum scenerio is that the wire is identical in length and type and running alongside the signal wire. This will minimize noise in the signal. If you dont run a current-return wire, you risk inducing a lot of noise, like your radio station for instance, or 60 Hz hum. As for shields that are unconnected, this is only possible in cases where there is already a signal and return wire present. There is no current running in the shield because it is only connected at one end and this provides a partial "faraday cage" that will prevent EMI from being picked-up by the internal two conductors.

"Audioengr, So, lets take a 60HZ signal and run it down the "Signal carrying" wire. Since this would be the same as a 60hz sine wave, are you trying to say that the positive half cycle goes down one wire and the negative half cycle comes back on the ground?"

No, what I am saying is that when there is a positive current flowing in the signal wire of an interconnect, there is an equal and opposite current in the "ground" or "return" wire.

We are talking about AC here. Hate to disagree, but I don't think so. Also, we cannot have current without voltage since volts push amps. In less than 120 volt applications, we have one line of potential(as in house wiring)and according to your described theory the ground(neutral) would also have be a hot wire since each half cycle would need to be equal with respect to volts and amps on each conductor.

No, the Neutral in house wiring is not ground (earth ground). Hot is equivalent to signal wire and Neutral is equivalent to return (which can be ground) in an interconnect. Current flows in both Hot and Neutral, but not in the earth ground. Since the ground for interconnects is also used as a return path, there will be current running in this one.

"In 35 years of being around electricity in various forms, I've never had the need to measure the ground except when we had an electrical "Short" popping people."

In audio systems, it is important to measure earth ground as the system usually comprises several components plugged into several outlets, which may be on different circuits. The result is that the various grounds can be at different potentials, which can result in hum due to current flowing in the power-cable ground wires. The fact that there are ground connections between components through the grounded power cords and also in the interconnects creates ground-loops by definition. This is unavoidable in "single-ended" systems.

Balanced signalling eliminates this problem becase there is an earth ground with no current flowing in it and two signal wires with equal and opposite currents. So, you see, the balanced interconnect is actually more similar to household AC wiring with Hot, Neutral and Earth Ground being similar to +, - and Ground.

BTW - I have 26 years experience as an degreed Electrical Engineer.

Bigtee wrote: "As I said before, you have the positive half cycle and then the negative half cycle that "Flows" the opposite direction on the same wire."

Correct, the current alternately flows in what I like to call the "forward" wire, but the inverse of that current also flows simultaneously in the second wire, which I call the "return" wire. In most AC power systems, this is NOT the ground wire, because this would violate electrical code, regardless of whether the circuit is single-phase or three phase.

Bigtee wrote: "On the output of the secondary, one side is tied directly to earth ground and also serves as the common for the wiring activating all the small 24VAC coils on relays. The other runs to the other side of the coils."

If this is the case, then for these internal circuits, the ground is used as a return path for the current. It would be difficult to measure any voltage drop across a grounded chassis, because the impedance is so low.

I actually worked as an industrial electrician apprentice while I was going to college 27 years ago, so I have some experience with electrical code, 3-phase, contactors and transformers etc..

Here are some more tips for you, since I design wires for my company:

1) interconnects should be low capacitance - this means spiraled pairs of small gauge wire that are spaced-away form each other. Use Teflon or air-filled dielectrics to separate and insulate them.

2) Speaker cables should be low inductance and low resistance. To get low inductance, you need coupling, so make many twisted-pairs of 20-24 gauge wire and then connect then at the ends to for a single circuit.

Works for me....

Stehno wrote:

would I need a ground? I know I should always have a ground but I am not using one right now. But all's I need for 230 volts is two 115v lines from opposing phases?

No, the ground is strictly for safety. It is not needed in the circuit, however it is well-advised to leave it attached. If you have ground-loops, it is safer to float low-power components to eliminate them, or use an isolation transformer.

why does a 20 amp or 30 amp cooktop or oven have two leads, 1 neutral, in addition to the ground? What's with the second lead in these appliances? Or is it the neutral I should be asking about?

I believe that some appliances use more than two legs from the transformer, or they have internally relays or motors etc. that need 117V with neutral. Not that familiar with appliances.

You say that the neutral contains the return current as I've heard this many times. But why is it that I can touch my neutral bus in the service panel and not feel a thing? What is different about 'return current'?

There is no potential on the neutral bus in the panel because it is referenced to ground there. All neutrals that return to the panel are referenced at a single point. There is a voltage drop in the wire from the component back to the panel, but since the neutral at the panel is tied to the ground at the panel there is no potential on the neutral at the panel. However, if you measure the AC voltage on the neutral at an outlet where there is a load attached, you will measure a small voltage. This is the voltage that is generated across the resistance of the neutral wire from the outlet back to the panel. This voltage on neutral at the outlet will exist only when current is flowing in the circuit. This voltage must be measured with respect to ground.