Why an AC Power Cord cannot make a difference

[Cbdb2]

We don't know how to test it because we don't know what differences power cords are supposed to make.

There supposed to make no difference. Which is what they do.

 

[Holmz]

My big power cord upgrade splurge, 14 AWG of hospital grade scrubs, arrives Friday.

How should I test it?

I've got a function generator, a digital multi meter, and an o-scope.

If you can keep from electrocuting yourself then one could digitize the voltage on the rails with respect to ground.
Play a track with cord-A, then with cord-B, overlay the two files if voltage versus time.
If both had no rail fluctuation then both are good.

Some of that could fall apart if he rails sag, as an amp with feedback could still operate up to whatever voltage is needed below the rails.
But it would be a start to see if anything is happening in the amp’s power supply.

RF and noise - might not be caught.

 

[kemmler3D]

We don't know how to test it because we don't know what differences power cords are supposed to make.

Measure the RF emission, measure step response or something, i don't know

First, come up with a metric for "depth of soundstage" or "velvety", or "blackness of background" (as distinct from noise level, somehow.) Then measure for that.

 

[wwenze]

First, come up with a metric for "depth of soundstage" or "velvety", or "blackness of background" (as distinct from noise level, somehow.) Then measure for that.

 

[watchnerd]

If you can keep from electrocuting yourself then one could digitize the voltage on the rails with respect to ground.
Play a track with cord-A, then with cord-B, overlay the two files if voltage versus time.
If both had no rail fluctuation then both are good.

Some of that could fall apart if he rails sag, as an amp with feedback could still operate up to whatever voltage is needed below the rails.
But it would be a start to see if anything is happening in the amp’s power supply.

RF and noise - might not be caught.

You want me to open up my amp for this?

 

[watchnerd]

There supposed to make no difference. Which is what they do.

Well in the name of science, there must be some null hypothesis or something to devise and test.

 

[solderdude]

How should I test it?

plug it in... see if the device powers up.
That's all the testing that can and needs to be done.
The device (cable) either works or it doesn't.

Well in the name of science, there must be some null hypothesis or something to devise and test.

If you want to test the cable bring it to an EMC lab and test the crap out of it and bring a generic cable too to have this tested as well.
You will get a report on all kinds of tests.
Will probably set you back $ 1k or so but you will have undeniable proof they do not measure exactly the same.
For any 'everything matters audiophile' this will be proof it sounds different.

You can also attempt to measure the voltage drop between 2 cables using a device with a heater and you can prove there is a small difference in resistance.
You can also measure the cable by shorting it on one side and use a power supply which you can set to a stable output current and run that current through the cable.
Then measure the voltage drop at the connector where you insert the current.
You can calculate DC resistance.
You will find a difference.... and have proof (mains)cables differ.

Then there is the sighted comparison... add that and you will have more proof for audiophiles that the cables 'sound different'.

Record the output of the device it is tested with with both cables. Then simply subtract the files and you will end up with a difference file that shows a difference (I can guarantee it will) and you will have more proof the cables sound different (the sighted comparison is for determining which sounds best and will be the more expensive one for sure).

What more testing do you want if you want to find a difference ?

Don't do a blind test with a statistical relevant amount of tries and expect to find a clear difference ... you won't find it but can use such a test to prove that 'blind tests are flawed'.

 

[pma]

EM radiation is easy to measure, you do not need to visit EMC lab. But it will be labeled as unimportant, here at ASR.

Testing radiation of 3 AC power cords (what are the ASR tests about??)

We could see several power cords tests here at ASR and frankly, I have to ask what are the tests like this one https://www.audiosciencereview.com/forum/index.php?threads/audioquest-nrg-x3-review-ac-power-cord.32257/ What is important? In my opinion, the aim of a good power cord is to minimize...

www.audiosciencereview.com

 

[kyuu]

EM radiation is easy to measure, you do not need to visit EMC lab. But it will be labeled as unimportant, here at ASR.

Well yes, no one has ever claimed that there can't be measurable differences between one power cable or another. You can easily achieve a measurable difference by using a thicker gauge, or using aluminum instead of copper conductors.

But of course that's not the interesting or relevant question. The question is if that difference can somehow result in a different output from the amplifier (or whatever other electronic component in question).

 

[Purité Audio]

Two identical components one with the fancy cord one without, instant switching unsighted.
Keith

 

[MatrixS2000]

We don't know how to test it because we don't know what differences power cords are supposed to make.

Measure the RF emission, measure step response or something, i don't know

I would capture right at the back of the speakers. If a power cord changed the sound, it would be seen here.

speaker terminals<—line level converter—>ADC

 

[Speedskater]

Actually the power cord is a small part of a series circuit that starts at that big power company transformer 500 or 1000 feet down the street.
And other homes may share part of that series circuit.

 

[watchnerd]

plug it in... see if the device powers up.
That's all the testing that can and needs to be done.
The device (cable) either works or it doesn't.


If you want to test the cable bring it to an EMC lab and test the crap out of it and bring a generic cable too to have this tested as well.
You will get a report on all kinds of tests.
Will probably set you back $ 1k or so but you will have undeniable proof they do not measure exactly the same.
For any 'everything matters audiophile' this will be proof it sounds different.

You can also attempt to measure the voltage drop between 2 cables using a device with a heater and you can prove there is a small difference in resistance.
You can also measure the cable by shorting it on one side and use a power supply which you can set to a stable output current and run that current through the cable.
Then measure the voltage drop at the connector where you insert the current.
You can calculate DC resistance.
You will find a difference.... and have proof (mains)cables differ.

Then there is the sighted comparison... add that and you will have more proof for audiophiles that the cables 'sound different'.

Record the output of the device it is tested with with both cables. Then simply subtract the files and you will end up with a difference file that shows a difference (I can guarantee it will) and you will have more proof the cables sound different (the sighted comparison is for determining which sounds best and will be the more expensive one for sure).

What more testing do you want if you want to find a difference ?

Don't do a blind test with a statistical relevant amount of tries and expect to find a clear difference ... you won't find it but can use such a test to prove that 'blind tests are flawed'.

It’s a luxurious $18 cord.

$1k for testing is steep.

I wouldn’t bother with a listening test

 

[watchnerd]

Actually the power cord is a small part of a series circuit that starts at that big power company transformer 500 or 1000 feet down the street.
And other homes may share part of that series circuit.

This just gives me another excuse, besides seasonal blackouts from storms, to get a generator

 

[Speedskater]

This just gives me another excuse, besides seasonal blackouts from storms, to get a generator

That seems like a solution, in search of a problem.

 

[kyuu]

This just gives me another excuse, besides seasonal blackouts from storms, to get a generator

Yeah but first you need to invent the market niche of audiophile generators. Don't want those dirty electrons from your average, pedestrian generator corrupting your premium audiophile electronics. Solar would be okay except it can make the sound too bright, and wind turbines can make the sound a bit too airy.

 

[Holmz]

You want me to open up my amp for this?

The arguments I have heard are that the power resistance cord lets the power in faster.
Which charges the amp faster/better.
Hence I would look at the rails.
As the rails are inside of the amp, it sort means that it needs to be opened up.

One could look at the amp’s output, and in that case either compare 1 cord to another, or compare either cord relative to the original signal.
I would do it the last way.
Once the digitized voltage at the speaker terminals are time aligned with the original waveform, then difference those two and do an FFT.

Note that the charge is coming out of the rectified at 120 Hz in your area, so I would be looking for harmonics of 120Hz, but you’ll get everything.

 

[watchnerd]

The arguments I have heard are that the power resistance cord lets the power in faster.
Which charges the amp faster/better.
Hence I would look at the rails.
As the rails are inside of the amp, it sort means that it needs to be opened up.

One could look at the amp’s output, and in that case either compare 1 cord to another, or compare either cord relative to the original signal.
I would do it the last way.
Once the digitized voltage at the speaker terminals are time aligned with the original waveform, then difference those two and do an FFT.

Note that the charge is coming out of the rectified at 120 Hz in your area, so I would be looking for harmonics of 120Hz, but you’ll get everything.

I'd rather not die for intellectual curiosity about an $18 power cord.

 

[BeeKay]

I'd rather not die for intellectual curiosity about an $18 power cord.

Just think of the epic inscription on the gravestone: "He did it for the team and for science. In loving memory, your ASR buddies"

 

[Holmz]

I'd rather not die for intellectual curiosity about an $18 power cord.

Well then … your intellectually curiosity needs work.

One could find someone to attach leads to the rails, and have a voltage divider circuit to get it down to the ADC level.

But I did word the way I did, in order to let people without basic electronics skills know it is not 100% safe.