Power Cables

I think that the following lengthy post that was provided by Atmasphere a few years ago, in a post dated 6-3-2014 in this thread, is worth quoting here in its entirety.  It reinforces some of the things that were said above by Steve (Williewonka), and by me earlier in this thread.

For those who may not know, Atmasphere (Ralph Karsten) is the owner and designer of Atma-Sphere Music Systems, which manufactures unique and very highly regarded audio amplifiers and preamplifiers.  He is also, IMO, one of this forum's most knowledgeable, experienced, helpful, sincere, and level-headed members.

With power cords its all about voltage drop across the cord. Some of that is at 60Hz, and some of that is much much higher- well above 30KHz-100KHz depending on the power supply in the unit with which it is being used.

I've seen a 2 1/2 volt drop rob an amplifier of about 30% of its output power. The cord was rated for 10 amps, and the draw was about 6 amps. This measurement was done with a simple 3 1/2 digit Digital Voltmeter.

The more insidious problem is high frequency bandwidth. The power supplies of most amplifiers have a power transformer, a set of rectifiers, and a set of filter capacitors. The rectifiers only conduct when the power transformer output is higher than that of the filter caps. So:

When the caps are fully charged the amp is able to play. As it does so, the caps are discharged until the AC line voltage waveform gets high enough again that the rectifiers in the power supply are able to conduct. Depending on the state of charge of the filter capacitors, this might only be for a few microseconds or it might be a few milliseconds. Either way, the charge is a spike which has very steep sides- and requires some bandwidth to make it happen.

If the power cord has poor high frequency response, it will current limit on these spikes. This can result is subtle modulations in the power supply or even a sagging power supply voltage.

Romex wiring found in many buildings actually works quite well. So it really becomes all about that last few feet and also how well the power cord is terminated- molded cords generally are not terminated very well. If the ends of your power cord get warm after a while, you know you have a problem!

This can be measured, its quantifiable and also audible as many audiophiles know. Anyone who tells you differently probably has not bothered to do any measurements- please refer them to this post.

I can go into more depth but this is it in a nutshell. Incidentally, Shunyata Research is refining an instrument that does a more in-depth analysis of what this is all about. At the link you will see that their tests essentially confirm what I have said here.

http://www.theaudiobeat.com/visits/shunyata_visit_interview.htm

Regards,
-- Al 

And from this thread, in 2010:

Almarg 9-15-2010

Power cords: a 2V drop across a power cord can rob a tube amplifier of as much as 40% of its output power!

Ralph, could you provide a technical explanation of why that would be so? I don’t doubt your statement, but I’m interested in understanding why that would occur.

Re your other points, all of which strike me as excellent, I think that it should be stated that none of those points NECESSARILY mean, to cite an example, that a $2,000 power cord will outperform a $200 power cord in any given system.

Atmasphere 9-15-2010

Al, the reason a power cord can have this effect is simple. If there is a 2 volt drop in a power cord, the filaments of the tubes will run cooler and the B+ will be reduced. Since this is a voltage, the result is we get less voltage output out of the amp. Less voltage=less power. Depending on the amp this can be pretty profound. and I have seen it with my own eyes. I do agree though that that does not justify a $2000 power cord, but it **does** justify one that has decent connectors and conductors that will not heat up at all. That has to cost something, probably not $2000 though. One thing about audio is that if there is a phenomena, there is also snake oil for it.

Almarg 9-15-2010

Thanks, Ralph.

That would also seem to say that the value of the ac line voltage at each listener’s location can be a very significant variable in the performance of a tube amp (assuming it does not have regulated filament and B+ supplies).

Which in turn emphasizes how easy it can sometimes be for extraneous variables to lead to incorrect sonic assessments.

Regards,
-- Al

Hey, how ‘bout an explanation how power cords can be directional? Or an explanation how they can’t would be fun, too. 😀

Pop Quiz: How come HDMI cables are directional?

Power cords are directional because one end is terminated to plug into the wall or power conditioner and the other end plugs into the audio equipment.  I can’t remember ever seeing one that wasn’t.

Really interesting that the article above says the wiring in the walls is usually pretty good.  

My Levinson 333 has no option to change the power cord.  I have wondered about running 30 amp service to it and swapping out the plug as specified in the manual.  I wonder if the difference would be audible for high-transient situations.

I have a couple of different power cords and look forward to trying them once my Stellar GCD arrives next week.

Why do folks insist that "Power Cables" need to have a bandwidth equal to that of a very high-spec amplifier’s audio bandwidth? Are you people INSANE? We are talking about 60Hz AC here!
If your power cords are carrying Khz range signals or noise there is something horribly wrong with your amplifier that needs to be corrected immediately, if not sooner because you are essentially operating a Radio Transmitter in violation of Federal Law! ;-)