An electrical engineer on how power cables can impact sound quality

High end power cables are cool things that appeal to the audio nut. If you like them buy them. I strongly doubt they make any difference in sound; the nuance here is to avoid the really cheap stock ones. Audio Science Review is the most clearheaded opinion on things like this. The fact that many of the people who like fancy cables are tube enthusiasts says it all.

I don’t fully agree.

For one I am not a power cable “believer”, but I suppose if I saw one make a difference then I could be.

Secondly, many tube amps in particular have massive reserves of energy. One can turn off the power switch and they play for many seconds with the same authority as with the power switch on. If the amp was not buffering the energy as a DC in capacitors, then we would hear 60 Hz coming out as the rails were pulsating with the incoming power. But that is pretty rare… I have not heard that happen myself.

The preference of tube amp harmonics is not really something that would preclude ASR membership. If one can show that SS harmonics are creating “off putting” sounds, then if those metrics show that tubes do not have those harmonics… then that it is also providing a science based reason why tubes might be preferred.

So let’s not convolve tubes with power cords, and lets not devalue objective measurements to be something that cannot be used to describe the sound of an amplifier in a system.

Lastly there are almost no measurements that show that an amplifier works better with such-n-such brand of a power cord. If the power cord makers showed a lower noise spectrum at the end of the cord, or that the amplifier had a more stable DC rail voltage, then it would be an easy way to claim that a difference exists and that there is a rational reason to consider their purchase…

I think that the power cords look cool, and have cool names, but I doubt they do much. And I await being convinced by something more than personal testimony and story-time lore.

@lanx0003 

What is lacking here is the actual testing / comparison before and after the luxuary power cable is used? Does the power get cleaner? I don’t think it is hard to do, right?😉 I believe the burden of proof is on whoever claiming the superiority of the cable.

That burden of proof is upon the manufacturer of the power cord if they try to get us to buy it.
Without supplying that proof, it is unlikely that we would be shelling out money for their unproven cable.

And if they had proof, I do not see why they would not be shouting it from the roof tops.

@audioguy85 Vandersteen power amps have 128 volt DBS for good reason :-) Enjoy your great cables !

Jim

I do not think that they are running that 128 or 72V on the power cable side though.

@Creutzfeldt-Jakob

Amplifier is only a black box between the PC and the speakers. PC provides the juice. If the instantaneous demand by the speakers are not delivered by the PC, the sound will be affected.

Why don’t we have a problem 60 to 120 times a second when the power company switches from sending voltage to retracting the voltage?

The voltage and current are alternating at 60Hz. The voltage is relatively constant at 120V, but the amplitude of the current pulse with the music. How closely this pulse can track the demand has an effect on the sound we hear. 

Brother, I seriously think you need an O-scope.

The incoming power voltage does a sine wave at 60 Hz (or 50 Hz)… it is not a constant 120V, it is an AC 120v.

The current is created as a consequence of voltage and the impedance of what it is “driving”. Even if the impedance is zero, the current at 0v is also zero.

What is happening with the music playing, and its effect upon the power reserve (capacitors), could also be viewed on an O-Scope.

If the power supply was being dragged down, then the 60 Hz (or 120Hz) of the power supply filling the capacitors would be pounding through the amp’s output.

 

My bad. It’s AC120.

Agree. As I have said earlier, the current is inversely proportional to the impedance. The impedance of the speakers changes with the frequencies of the music, so the amount of instantaneous current drawn by the speakers follows the music.

^That^ is all true.

The question is whether the incoming power, to refill the power supply capacitors, makes any difference on what is happening on the outgoing power to the speakers.

And if so, can it be shown objectively/quantitatively?

My hypothesis is: difficult to drive speakers are more sensitive to the quality of the PC and vice versa. Opinion?

If there was a difference, then it should be happening when there is more need to have greater current flowing in. So ^your hypothesis^ makes sense.

if the electrical signal coming out of the amp was changed (like playing the same content and comparing the captured signals), then we would know that there is a real difference.
How hard would that be to do?

I tried power cords with neodymium magnets on both ends by the plugs on my power-amp (I don't know what other mechanisms in the power cords were at play).  Even before I dropped the needle on the album, I noticed a slightly blacker background and when playing music, I did notice a slight improvement in micro-detail (m I assume due to the lower noise-floor).

If there was a reduction of noise with no Musial signal, then it almost seems like we could measure the RMS AC noise at the speakers and see it then? 

You can,  use a sensitive multimeter (4-1/2 digit) for an absolute value that can be converted to dB, or a good, sensitive audio measurement system like REW to listen to the speaker in a close-miked manner... usually at the tweeter since this is where the abundance of noise lives.

Thanks @piaudiol I just do not hear anything when the volume is up, but there is no content.

If I heard hissing abate when the thing was plugged in, I would be a believer, but maybe I am lucky as it cannot get darker than pitch black. Or maybe my hearing is bad or my background noise level is too high to hear it, or the power is good where I am at?

I have no experience like this description:

Even before I dropped the needle on the album, I noticed a slightly blacker background

@piaudiol 
So I guess the inclusion of the video is implicitly meant to convey that your gear was not measurable as different, and could only be heard as different?

 

An aside for anyone using a Mac computer for a music server: try listening with the stock power cable. Then, invert the polarity of that cable (easy because of the IEC C7 connector). Then report back what YOU hear. I never comment on what, if any, differences will be heard. I don’t want to influence confirmation or anticipation bias. This is what A/B listening tests are all about. Have a friend help to eliminate any bias.

At some point, since music enjoyment is the goal, we have to trust our ears and preferences or find another obsession

@piaudiol 
Ok this is timely.

My main source is the TT.
However, I have an old CD player (90s), and a new AVR that can act as a Roon end point, and then I can plumb that into the preamp.

If I used the MAC would that be with 1/8” to RCAs?
Or over ethernet to the AVR?
(And does it work on an Intel NUC as a Roon server?)

On the MacBook (laptop) the IES goes into a power supply which plugs into the computer as a DC source. SO flip that 180? Or does it need to be into something without the AC—>DC converter?

I'm not sure how power polarity affects the wall wart supplies.  They are very different from the Lite-On supplies in the mini.  My power cable was specific to the Mac mini.

Ok I am with you now.
I’ll disregard, as I don’t have the small Mac.