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

For those who wonder how a power cord can make a difference, consider this: an amplifier has a power transformer, rectifiers and filter capacitors in its power supply. Normally, the filter caps are charged by the rectifiers as the transformer makes voltage.

When the filter caps are nearly charged, the only time that the rectifiers will conduct is at the peaks of the 60Hz input waveform. So all the energy going into the amp is concentrated at the peaks. This is the point that the diodes turn on, as the voltage on them is higher than the voltage on the filter caps.

As soon as the wave is past peak, the rectifiers will turn off, when the filter cap voltage is higher than the voltage from the rectifiers.

So the energy going into the amp is often doing **only at the peaks**. The difference between a cheap power cord and an expensive one, in terms of its ability to dump large amounts of current during these peaks is only about 3%. It is that 3% that audiophiles hear.

A second phenomena is AC voltage drop across the cord. We have measured nearly 3 volts in some cases. In a 100-watt amplifier that can account for a nearly 50% DROP in power!!!

If you think these two phenomena are not audible you're missing a bet. The bigger the amp (IOW the more power drawn), the more audible power cords become.

We figured some of this stuff out nearly 20 years ago, which is why one of our bigger amps (the MA-2) actually runs two power cords per chassis (since there are 2 AC circuits in the amp for 2 power transformers) to limit the audible effects of the power cords. Back then there were not nearly so many exotic cords as there are now! -so we had to make do and adding a power cord worked out very nicely.

Ralph;are there any cords that work better with your amps
that you like as a preference;you already gave me great advice on the Mogami balanced cables so I thought I would ask on the cords.

Hi Ralph,
Not to "stir the pot" here, but to simply try and learn something; isn't your discussion largely related to resistance, and isn't that largely related to the gauge of the PC conductors and the length of the PC? Can a power cord achieve the "ability to dump large amounts of current during these peaks" simply by having adequate gauge conductors (say 10awg) and tight fitting connectors? Assuming noise is not an issue, are there characteristics other than the ability to transmit current that you believe to be important?

Thanks for that, Ralph! That's the most concise and clear explanation I've read on the subject.

A couple of questions:

What accounts for a 3-volt drop across an AC cord? How does that happen? Is this an argument for shorter power cords? Is it all in material and design?

Why/how can one power cord dump more current at the peaks faster than another? Isn't this limited or affected to some degree by the power source (the AC), and how that source is delivering power? I think (perhaps erroneously) about the analogy of a hose delivering water - no matter whether the hose is fat or thin or obstructed or not, it will always be limited to some degree by the delivery of the water from the spigot. If the water is being delivered in spurts and fits, the hose will not change that.

Every 200+ Watt per channel amp that I have owned came with extremely thick stock power cords. I think Ralph is on to something there. Power cords are important when it comes to high power output devices.