or Connect
Head-Fi.org › Forums › Equipment Forums › Sound Science › Power cable testing
New Posts  All Forums:Forum Nav:

Power cable testing

post #1 of 49
Thread Starter 

Hi guys, sorry if this thread already exists somewhere but I couldn't find one.

 

Who out there has actually tested a range of power cables with a cathode ray oscilloscope?  What did you find?  I mean, if you plugged a CRO into a power outlet in your house and look at the waveform and see noise or harmonics, then plug the CRO into the same powerpoint with a $1000 power cable and observed the difference in the quality of the sine wave?  

 

As an experiment you could plug in a CRO, then plug in an air compressor or grinder or something with a big dirty motor on it into the other socket on your double powerpoint and introduce a bit of noise into the supply and note the changes to the fundamental frequency, then repeat the test with a new beaut power cable, you would either see a difference or you wouldn't, right.  And that would be a difinitive result?
 

And also, if you have a noisy power supply does it make a difference to the sound produced anyway?  I wonder if any of the people or companies that do frequency response graphs and the like are in an industrial estate - hopefully with a cabinetmaking business or something a couple of tennancies away from them that are using saws and thicknessers and sanders and the like all day.  What would happen if they tested a certain system during the day when there is lots of dirty loads on the power grid then repeated the exact same test after hours when everyone had finished up for the day and gone home and the power supply was cleaner - does the system sound 'better' in the middle of the night?
 

Surely someone out there has done something like this.... ? 

post #2 of 49
Quote:
Originally Posted by mulder01 View Post

 

And also, if you have a noisy power supply does it make a difference to the sound produced anyway?

I doubt, since electronics transform input AC to DC immediately. It would be interesting if someone did an experiment by adding some noise (much higher level than it ever happens naturally) to input power, and then perform typical amp/dac/headphone measurements to see if there is any difference.

post #3 of 49

 a "cable" is and should be a passive conductor. people work to make proper cables for each purpose with one thing in mind, and only one thing:
carry the signal on the desired distance with minimal change to it. that is the purpose of a cable.
if something filters the existing signal, then it's not a cable anymore and it's not doing what I'm asking of it. I see no point in going past that.

 

 whatever the "cable" does to the signal, it could be done inside the amp/dac/prius/coffee machine...
why not let the manufacturer decide what to do with the power signal? I have that slight incentive that the guy building a machine might know best what he needs to do to for his machine and doesn't wait for clever boy to put a few components in a cable and sell that a 1000$.

post #4 of 49
Thread Starter 

Yeah, I am an electrician and I realise the whole idea of fancy power cables has no real theory to back it up, I mean if using a premium power cable was advantageous in any way, why wouldn't manufacturers of $5000 amplifiers include a $80 power cable instead of a $3 power cable to push their equipment to it's full potential.  I mean, it's plain to see that the people who have the smarts to actually design this stuff have no faith in them either, but I was just wondering if anyone had actually ever tested them with a proper meter, just for some actual readings and hard data, rather than everyone just saying their opinion based on their level of knowledge.

 

I mean, from what I understand, people use premium cables for the audio signal to make sure that every little last micro watt flowing through that cable arrives at the other end exactly the same as it entered with maximum accuracy, but don't you want the opposite with the power cable?  If the aim is to REDUCE all the little noisy lumps and bumps wouldn't you want a slightly ****ty conductor that will possibly lose a bit of those unwanted 'details'?

post #5 of 49

I like to think that if the magnitude of improvement was anything actually interesting, then it would be standard procedure at least on all expensive models that don't need to cut specs to save money. it's just as you say.

 

but why not, for curiosity purpose only. 

then what needs to be tested if the actual impact on the output audio signal. not just how well the power cord filters something, as we have no idea if that filtered part would reach the audio signal anyway(making the process even more useless than it already seems to be). I'm tempted to think that just going from AC to DC would already deal with a lot of low level noises.

post #6 of 49

Because power cords can and do act as interference antennas (both receiving & transmitting) any occasional audible difference will be very situation specific.

It can involve:

Other components in your audio system.

Nearby appliances or lighting systems.

Length of all nearby cords.

Dress or path of all nearby cords.

 

Note: This interference can be a challenge to measure because just adding test equipment can change the situation enough to invalidate the measurement.

post #7 of 49
Quote:
Originally Posted by mulder01 View Post

Who out there has actually tested a range of power cables with a cathode ray oscilloscope?

You said you're an electrician, so this is more for others reading: What can be seen at the end of a power cord on a 'scope is irrelevant. All that matters is how the connected audio device is affected. Even if there's several volts of noise and RFI riding on the AC line (unlikely), and even if some overpriced aftermarket power wire filters that out, that doesn't mean the expensive wire will be audibly better than a normal wire.

This is a common ploy by wire vendors. Most show no data at all telling people to "just listen." But when they do offer "data" it's a 'scope on the AC wire, and never a 'scope or noise measurement at the output of the connected audio gear.

--Ethan
post #8 of 49
Wouldn't the test of pressing the "on" button be sufficient to judge if a PC is working up to spec?
post #9 of 49

If you get power line noise from refrigerators or air conditioning units, it's MUCH more likely a problem with your house's wiring than your stereo's.

post #10 of 49
Thread Starter 
Quote:
Originally Posted by Speedskater View Post
 

Because power cords can and do act as interference antennas (both receiving & transmitting) any occasional audible difference will be very situation specific.

It can involve:

Other components in your audio system.

Nearby appliances or lighting systems.

Length of all nearby cords.

Dress or path of all nearby cords.

 

Note: This interference can be a challenge to measure because just adding test equipment can change the situation enough to invalidate the measurement.

I take it that from what you just said that you're a believer in the benefits of premium power cables, but from what you're saying, if you keep your power cables short and away from signal cables and don't put your gear right next to fluro lights and air conditioners etc then you've pretty much done the equivalent of a very expensive power cable upgrade?  I mean, back when I had a home stereo setup I had my gear on a rack that had a back on it and I ran all my signal cables just behind the equipment, in front of the backing part and ran all the power cables right around the back to keep the segregation.  Surely that is easier, cheaper and better than running a fancy shielded power cable parallel with your speaker wire,

post #11 of 49
Quote:
Originally Posted by mulder01 View Post
 

I take it that from what you just said that you're a believer in the benefits of premium power cables, but from what you're saying, if you keep your power cables short and away from signal cables and don't put your gear right next to fluro lights and air conditioners etc then you've pretty much done the equivalent of a very expensive power cable upgrade?  I mean, back when I had a home stereo setup I had my gear on a rack that had a back on it and I ran all my signal cables just behind the equipment, in front of the backing part and ran all the power cables right around the back to keep the segregation.  Surely that is easier, cheaper and better than running a fancy shielded power cable parallel with your speaker wire,


No, just the opposite!  I would never buy a premium audiophile AC power cord or cable.

What I'm saying is that vary occasionally differences are heard, but it will be very situation specific!  Change the length of a cord or turn off another component or do something else and the noise may change. The cord is often not the true cause of the problem and only by luck does the cable quite the problem.  That is until the situation changes then you may have a new problem.

Jim Brown and Bill Whitlock write about AC cords & cables from a noise or interference point of view.

post #12 of 49
Quote:
Originally Posted by mulder01 View Post
 

Hi guys, sorry if this thread already exists somewhere but I couldn't find one.

 

Who out there has actually tested a range of power cables with a cathode ray oscilloscope?  

 

I've done better than that.  I went through the trouble with my group of conducting a bias controlled listening test of power cables.  To make a long story short, common sense is correct.  Power cords have no affect on system sound.

post #13 of 49

I salute you. I didn't have the patience to reach back that far to test. I started with interconnects.

post #14 of 49

same. when I find something really obviously irrelevant I usually don't experiment. that said, I always wondered if some birds were able to breath underwater? cause you know, science is lying to us about cables, measurements, dacs, black holes in cyclotrons, climate change, WMD in irak(Weapons of Mass Distortion)... so why not lie about them birds? maybe most can't, but that doesn't mean that no bird can breath underwater!

think I'm getting a hang on audiophile counter logic. ^_^

 

about power cables, from my point of view, if having a dirty power signal was to affect in a major way the output quality of my amp. then I would conclude that my amp is crap and blame the manufacturer for not thinking this might occur and taking care of it.

I would never go get a wire with a pass filter for 1000$. for that money I'll get myself an amp that doesn't mind the dirty power signal. or maybe I'll pay someone to take care of that for my entire house, not for 1 amp.

post #15 of 49

When I was building my theater/listening room, I had the electrician add a dedicated circuit to my stereo and projector. That way it was isolated from refrigerators and dimmer switches.

New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Sound Science
Head-Fi.org › Forums › Equipment Forums › Sound Science › Power cable testing