Why manufactures don´t burn in their amps and ...

Power cords are important when it comes to high power output devices.

True. But along the lines of Mitch2's comment, all of the effects mentioned in Ralph's post can be avoided simply by having adequately low resistance in the path between outlet and power amp. Which often may not be provided by stock power cords, but can certainly be accomplished via a modest upgrade that does not utilize exotic materials and construction techniques and cost megabucks.

We have measured nearly 3 volts in some cases. In a 100-watt amplifier that can account for a nearly 50% DROP in power!!!

Ralph -- Can you elaborate on how such a large drop can occur, and if that would hold true just for tube amps with unregulated filament supplies, or for tube amps with regulated filament supplies and/or solid state amps as well?

Thanks,
-- Al

Stewie: "(Mr. T): this hobby is so subjective that when you have 2 audiophiles in a room, you will get three opinions."

That's nonsense. You will get four opinions.

True! After the first one changes his mind, the other one will follow suit.

Shadorne: And indeed that is what I have found to be the mystery around those extremely thick stock power cords that came with the higher powered power amps (at least those that I have been familiar with). Thick cable was not just all rubber/plastic but they came with thicker wires too!!!

Nice to see that at least some of our members can bring a sense of humor to this subject :)

-- Al

Magfan -- Despite the claims that some cable manufacturers may make in their marketing literature, I don't think that a power cord can have a significant power factor, because its inductive reactance and capacitive reactance at 60Hz will be completely negligible. Although I agree that the power factor of the load can certainly be significant, which would presumably be inductive due to the power transformer.

Using this inductance calculator, the inductance of say a 72 inch power cord of any reasonable gauge is in the range of 2 to 3 microHenries. That is roughly a milliohm (0.001 ohms) of inductive reactance at 60Hz, which is negligible both in absolute terms and in relation to the load (and undoubtedly also in relation to the house wiring inside the walls, as well!).

Capacitance will vary widely with the power cord design, but as a very worst case guess let's assume 1000 pf/ft. At 60 Hz, for a 6 foot cord, that would be a capacitive reactance (in parallel; therefore the higher the better) of about 500,000 ohms, again totally negligible both in absolute terms and in relation to the load impedance.

Regards,
-- Al

Excellent points, Ralph. Thanks!

Re Googling "spark coil," I think that also Googling the term "inductive kickback" would further reinforce your recommendation about shielding.

To make sure it's clear to the others, inductance (which is present to a considerable degree in a transformer) resists abrupt changes in the current flowing through it. If the current flowing through it is forced to change abruptly, such as by the rectifier commutation Ralph describes, the result can be extremely large voltage spikes, resulting in high frequency noise that can radiate through the air as well as couple through circuit paths.

Regards,
-- Al