Twisted or Straight?

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.

Ozfly:

One of the electrical engineers who frequent our site may shoot me down on this, but I honestly don't think it will make any difference -- from an audibility standpoint -- whether you run twisted or parallel power cords from the panel to the outlet. Please note that I am not saying that there aren't valid electrical transmission issues that should be considered -- only that they should not be audible.

The electric current that will be coming out of the wall precedes any signal, and the AC power is going to be reduced in voltage by the transformer in your power amp, and then rectified from AC to DC current. Hence, concerns like inductance and capacitance should not be of any concern with your house wiring. Once the audio signal leaves the amp on its way to the speakers, however, the behavior of the speaker wiring with regard to capacitance, inductance, and characteristic impedance can be a real issue, which is one of the reasons there are so many approaches to speaker cable design.

Audioengr, Nice to see your page! What is the overall inductance impact on 12AWG 2m power wire that passes 60Hz from the wall?

X(reactance) = sqrt(2*pi*60Hz*L)

In this formula L is in microHenries range and reactance on 60Hz is just tens of miliohms so the voltage drop due to inductance is realy measurable. The AC deviations are much higher than the voltage drop due to the inductance isn't it?

After all how the low-inductive power cord will be different from high-inductive one if the bottom line is that the signal is being rectified and decreased and sometimes internally stabilized.

What anywhay the good quality power cord can do except reducing the noise, microphonics and AC impact?

Without even questioning the scientific reasoning & recommendations of cable designer Mike VansEvers I went with the twisted 10awg THHN solid copper, installed in grounded Greenfield (flexible metal conduit) for shielding. This works so well that I haven't even bothered to try out anything else so I can't actually compare, but can attest to my own very satisfactory results.
Mike told me to tape all 3 conductors together, then clamp one end of the bundle in a vice & the other end in a variable speed drill chuck. I aligned the printing on all 3 conductors in the same direction before twisting them up. It winds up like a big spring & then unwinds somewhat when the drill is powered off, so I then exchanged ends & better re-twisted the remainder. The load end is now terminated with a Wattagate 381 outlet, which from a sonic standpoint completely obliterated the 20A industrial Leviton outlet that was previously in place.