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Twisted or Straight?

I searched Audiogon for info on inductance and capacitance. From an excellent post by Sean on March 24, he explains that inductance increases with wire spacing ant that capacitance increases as wires move closer together. Therefore, a twisted pair raises capacitance as contact between wires is increased. On the other hand, I'm a bit confused in that I thought winding wire would increase inductance.
Here is my question: For an ac power cable running from the panel box to the outlet, would it be better to run twisted wire or straight (i.e., parallel) wire? Specifically, I'm referring to twisting the hot, neutral and ground vs. having them run parallel? I've read strong preferences for both. Per Subaruguru's post, straight romex increases inductance and allows unwanted high frequencies to roll off. Other posts suggest that twisted is better. Please help me sort this out since I am running dedicated lines to my stereo. Thanks in advance.
ozfly

Showing 3 responses by audioengr

audioengr
3,282 posts
 
Close spacing is the key to low inductance. Twisting two conductors together causes then to be in intimate contact over the length and therefore will result in lower inductance. Parallel wires, if in tight contact will also have low inductance. It is just easier to twist them to get the close spacing. ROMEX has a large spacing between the conductors and therefore has high-inductance. I have a table on my website that compares the inductance of ROMEX and various cords. See the Power Cable page at:
http://www.empiricalaudio.com

BTW, the best construction is to use solid 12 gauge THHN wire twisting the hot and neutral together and then twist the ground around them in the opposite direction. Put this inside a plastic conduit to meet code.
audioengr
3,282 posts
 
Marakanetz - The di/dt currents in the power cord are what matters. IF it is too inductive, the drops can be in the Volts, not mVolts. I have one of the lowest inductance cords on the market and it is getting rave reviews when used with power amps. If you read my description on my poer-cord page, it describes how the voltage drops can occur. Poor power cords can have the same effect that plugging into multiple power strips has, except on transients. If your amplifier has switching supply, the impact of a low-inductance power cord may be much less, because of the regulation.

BTW - twisting the two current-carrying wires has the additional benefit of radiating a smaller magnetic field that can impinge on nearby interconnects compared to two parallel wires.
audioengr
3,282 posts
 
This is really the way to do it. It keeps the grounds pretty much at the same potential and the lengths of each conductor about the same. Ground-loops is the biggest concern when running multiple circuits.
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