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

pma

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We could see several power cords tests here at ASR and frankly, I have to ask what are the tests like this one
What is important?

In my opinion, the aim of a good power cord is to minimize radiation of EM fields to the nearby audio signal cables. As I have been dealing with this for many years, I have decided to share some experience here.

The test
3 different power cords were chosen for this quick test:

1) standard PC 3-wire power cord with IEC plugs
2) same as (1) but shielded, a shielded cable for PC that we can buy at about $20
3) VDH Mainsstream Hybrid power cable with IEC plugs

The power cords were connected to my class D Hypex NC252MP power amplifier (it has integrated SMPS on board) and the EM field near the power cable was measured with a small loop probe, that will be seen in the images below. The signal from the loop probe was sent to E1DA Cosmos ADC and digitized at Fs=192kHz and displayed in ARTA.

Standard power cords (1) or (2) and the loop probe
Loop_stdcord.JPG


VDH power cord and the loop probe
Loop_VDH.JPG



Measurements with the amplifier turned off

All 3 power cords gave the same result as follows
Loopprobe_stdpwrcord_ampoff.png



Measurements with the amplifier turned on

1. Standard unshielded power cord
Loopprobe_stdpwrcord_ampon.png



2. Standard shielded power cord
Loopprobe_shldpwrcord_ampon.png



3. VDH Mainsstream Hybrid power cord
Loopprobe_VDHpwrcord_ampon.png



Conclusions

Though the standard unshielded and shielded "PC" power cords ($5, $20) have measured same and shown no effect on radiated field, VDH Mainsstream Hybrid cable has effectively limited the radiated EM field that was a result of NC252MP+SMPS operation at idle. More measurements might be interesting at high power load. It should be considered what to measure when testing the power cords.
 

antcollinet

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Do you think it is possible that the large diameter of the VDH cable might be relevant and likely greater distance between loop antenna and internal conductors (inverse square law and all that)?

Would it be worth putting some tape around the cheaper cords in the region of the antenna to simulate the same diameter. Or just use a spacer to move it an appropriate distance from the thinner cables?
 

HarmonicTHD

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We could see several power cords tests here at ASR and frankly, I have to ask what are the tests like this one
What is important?

In my opinion, the aim of a good power cord is to minimize radiation of EM fields to the nearby audio signal cables. As I have been dealing with this for many years, I have decided to share some experience here.

The test
3 different power cords were chosen for this quick test:

1) standard PC 3-wire power cord with IEC plugs
2) same as (1) but shielded, a shielded cable for PC that we can buy at about $20
3) VDH Mainsstream Hybrid power cable with IEC plugs

The power cords were connected to my class D Hypex NC252MP power amplifier (it has integrated SMPS on board) and the EM field near the power cable was measured with a small loop probe, that will be seen in the images below. The signal from the loop probe was sent to E1DA Cosmos ADC and digitized at Fs=192kHz and displayed in ARTA.

Standard power cords (1) or (2) and the loop probe
View attachment 230454

VDH power cord and the loop probe
View attachment 230456


Measurements with the amplifier turned off

All 3 power cords gave the same result as follows
View attachment 230457


Measurements with the amplifier turned on

1. Standard unshielded power cord
View attachment 230458


2. Standard shielded power cord
View attachment 230459


3. VDH Mainsstream Hybrid power cord
View attachment 230460


Conclusions

Though the standard unshielded and shielded "PC" power cords ($5, $20) have measured same and shown no effect on radiated field, VDH Mainsstream Hybrid cable has effectively limited the radiated EM field that was a result of NC252MP+SMPS operation at idle. More measurements might be interesting at high power load. It should be considered what to measure when testing the power cords.
How does your test and its results correlate to the audibility of signal changes in real RCA, XLR cables?
 
OP
pma

pma

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I have repeated the measurements with the amplifier playing 1kHz signal in one channel, 1 x 100W/4ohm/1kHz. Now only with a standard unshielded power cord and with the VDH Mainsstream Hybrid power cord.
With the standard power cord, we can see that the radiated B (magnetic induction) is increased. With the VDH power cord, we get the clean record, even without the small ultrasound peaks that were there yesterday. Should be noted that the record without 100W sine (idle) and 100W sine has been identical today.

Standard power cord, loop voltage, amp 100W/4ohm/1kHz
Loopprobe_stdpwrcord_amp100W4R.png



VDH power cord, loop voltage, amp 100W/4ohm/1kHz
Loopprobe_VDHpwrcord_amp100W4R.png



So there is no question, the VDH cable does the job and no laughter on "audiophile snake oil" is needed in this case. It is up to everyone to consider the price/improvement effect. It is not cheap, but if someone wants it, it might be one of the thousand little improvements in his system.

Loop probe induced voltage relation to EM magnetic induction

mag induction.png


S ... loop probe area
u ... loop induced voltage
B ... magnetic induction [T, Tesla]

The bigger the probe (loop) area, the higher induced voltage.

There is another interesting observation - the spectrum of B radiated field measured in the proximity of the standard power cord is in a complete accordance with the shape of the mains spuriae measured at the output of NC252MP as a noise background.

VDH Mainsstream Hybrid power cord
VDH_powercord.jpg
 
Last edited:

antcollinet

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I have repeated the measurements with the amplifier playing 1kHz signal in one channel, 1 x 100W/4ohm/1kHz. Now only with a standard unshielded power cord and with the VDH Mainsstream Hybrid power cord.
With the standard power cord, we can see that the radiated B (magnetic induction) is increased. With the VDH power cord, we get the clean record, even without the small ultrasound peaks that were there yesterday. Should be noted that the record without 100W sine (idle) and 100W sine has been identical today.

Standard power cord, loop voltage, amp 100W/4ohm/1kHz
View attachment 230567


VDH power cord, loop voltage, amp 100W/4ohm/1kHz
View attachment 230568


So there is no question, the VDH cable does the job and no laughter on "audiophile snake oil" is needed in this case. It is up to everyone to consider the price/improvement effect. It is not cheap, but if someone wants it, it might be one of the thousand little improvements in his system.

Loop probe induced voltage relation to EM magnetic induction

View attachment 230569

S ... loop probe area
u ... loop induced voltage
B ... magnetic induction [T, Tesla]

The bigger the probe (loop) area, the higher induced voltage.

There is another interesting observation - the spectrum of B radiated field measured in the proximity of the standard power cord is in a complete accordance with the shape of the mains spuriae measured at the output of NC252MP as a noise background.

VDH Mainsstream Hybrid power cord
View attachment 230577
Again - it seems to me possible that the improvement simply comes from the diameter of the cable. Your antenna may only be a couple of mm away from the conductors on the thin cable, with the thicker cable (by eye aprox double the diameter), it could be 4 or 5 times that - sufficient for the reduction you are seeing.

If this is the case, then no need for an expensive cable. Just make sure there is 10mm distance between power and audio cables - or put a thick "sock" around the cheap cables.

This is before even considering audibility pointed out by others.
 

Blumlein 88

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Is this audible? Can you demonstrate that the radiated noise is transferred back into the audio signal?
The thread title is what are ASR tests about for AC power cords. You have the key point here. They are about whether cords are audible. Lowering the radiated energy as is being tested doesn't show us the answer to that question. This needs coupling with measurements at the output to see if there is an audible difference.

Having tested some interconnects wrapped around PC power supplies I can tell you some audible artifacts happen with some RCA cables. Move them an inch way and they are measurable, but not audible and 6 inches away there are none above the noise floor. Use balanced cables and you get nothing even wrapped around a noisy PC power supply several times.

It is very possible that they only or main difference here is the thickness of the power cord. Measurements need to be done with the amplifier output or even a DAC near the power cord to see if anything gets thru. I have no reason to think it will unless the cable is unshielded RCA and directly in contact with the power cord. The easy answer isn't to buy an expensive power cord. The answer is to dress your cables or go balanced.
 

DJ_Rix

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Hi Pavel, nice test ! Would be nice to test Supra Lorad with same setup. Im really curious how Supra stick with they statements about EMI radiation.
I can provide one Supra Lorad 2,5 for test if you are interested.
 
Last edited:

Head_Unit

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There is another interesting observation - the spectrum of B radiated field measured in the proximity of the standard power cord is in a complete accordance with the shape of the mains spuriae measured at the output of NC252MP as a noise background.
I think that is not shown?
(1) I think folks need to relax a bit about the audibility, I see this as a "what if" experiment. Patience patience
(2) Having in college had problems we eventually traced to on.off radiated crap from a mini fridge, I think this is an interesting subject
(3) To contradict myself from #1, I then ask, what DOES the output spectrum of your amplifier look like? Because yes the big problem with exotic cables is nobody ever shows any AUDIO difference, and by these days we can investigate the most minute changes in waveform, no more bullish!t about mysterious unmeasurable stuff. (OK, maybe we don't know how to "measure" soundstaging blah blah however that is in the acoustic domain, at this point we can compare electric waveforms down to the Planck Constant...)
 

Head_Unit

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Your twist tie is not audiophile quality. You need to upgrade from ferrous metals to OFC. ;)
No no no, it must be plastic, handmade from only the finest Venezuelan light sweet crude oil, which is light and sweet because the climate was very temperate so the dinosaurs back then were always in good humor. You have to stir the mix with special "six nines" gold spoons in between each crack of the raw product...
 
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