At What Point Does Reducing Electrical Noise Reach No Audible Difference?

[toddalin]

Widget and I were having an interesting discussion of the merits of power cables and I told him that I could reduce electrical background noise by a few dB simply by rearranging the power cord to the surge protector. This is shown as the background electrical noise level on the Behringer RTA with a noise floor of -113 dB. Granted we are talking background electrical noise on the order of -100 dB and if you are sitting in a room at an ambient level of ~30 dBA, would you even be able to identify this change?

This month's Stereophile Magazine auditions the Naim preamp with a separate/or not power supply. The external power supply is shown to completly remove a/c power-related spuriae (sp?), but with the onboard power supply, these spuriae are down at -115 to -120dB. Yet, those performing the audition were able to tell there was a difference and overwhellingly preferred the remote power supply.

So what does this tell us???

[Mr. Widget]

This month's Stereophile Magazine auditions the Naim preamp with a separate/or not power supply. The external power supply is shown to completly remove a/c power-related spuriae (sp?), but with the onboard power supply, these spuriae are down at -115 to -120dB. Yet, those performing the audition were able to tell there was a difference and overwhellingly preferred the remote power supply.

So what does this tell us???

It tells us that their test was not a valid one.

If they had conducted the same test as a double blind test similar to the system used at Harman/JBL to test loudspeakers, I am quite confident the preferences would have been shown to be equivalent to random selection.


Widget

[toddalin]

Does it?

With the NPX 300 power supply

"After listening for a long time as a system with the NPX 300 power supply, we removed it, listened, then put it back. And then we assessed the difference.

Undeniably, this power upgrade works. We liked what we'd heard without the upgrade, but with it was obviously better, in almost all aspects of sound quality, including the headphone output. You need to hear it for yourself to fully comprehend the effect, but my team was obviously keen on the gains, surprised at the sound quality upshift, and demanding replay of many of the tracks previously heard to reinforce their appreciation of this augmented configuration. Further backtracking, to operating the 222 on the internal supply, confirmed this was no mistake nor overreaction.

If I had to put a figure on it, the uplift was some 20% of the extant system quality. The streaming sound quality of the NSC 222 had moved unmistakably closer to that of my ND 555 dual-supply reference DAC, while all the facilities benefited, both the LP disc input/equalizer and the headphone output."

https://www.stereophile.com/content/...0-power-supply

External power supply:
https://www.stereophile.com/images/0...2fig04-600.jpg

Internal power supply:
https://www.stereophile.com/images/0...2fig05-600.jpg

[Mr. Widget]

Does it?

Yes.

Just as eye witness accounts have been proven to be unreliable in court cases when hard facts like DNA evidence contradict them. We humans are a fallible lot.

Just because a room full of well meaning reviewers come to a conclusion, it doesn't mean a thing if their sighted bias is not eliminated. Even professionals have proven time and time again that their conclusions do not stand when tested in controlled experiments.

I realize this is hard to imagine. Just like you and I imagine virtually everyone else on this forum, I have heard definite improvements when none should exist. Our auditory perceptions are remarkable, but they are also quite fallible and often mislead us when we look for "improvements."


Widget

[mmc8180]

In every statistically valid test (which needs to be double blind based) in virtually any subject, humans have a low correlation of reliably detecting minute differences in anything using senses. That includes audio.

That fact is why I find no credence in audio reviews, other than for perhaps technical information or functionality.

[rusty jefferson]

It tells us that their test was not a valid one.

If they had conducted the same test as a double blind test similar to the system used at Harman/JBL to test loudspeakers, I am quite confident the preferences would have been shown to be equivalent to random selection.


Widget

I just read the article and agree it's inappropriate to throw out such a completely subjective assessment especially since there were 4 participants and making the changes necessary for a double blind A/B/X test would have been simple and only taken a half an hour for 1 participant.

That said, I image this upgraded external power supply would probably have distinguishable improvement on sound quality particularly because of all the digital components inside the chassis that are extremely sensitive to electromagnetic interference from the internal power supply. Also, I'd imagine the outboard supply has more and probably higher quality filter capacitance and regulation. I also didn't see any comments about whether the internal and/or the external supplies are linear or switch mode, the latter being potentially problematic with digital components. Either way, I think it's reasonable that a trained listener could successfully pass a double blind test in this instance assuming the system is otherwise transparent and listened to in an appropriately set up and treated room commensurate with the expense of the equipment involved. I'd imagine the sound would be more dynamic and also more relaxed (from reduced jitter) using the external supply. It's unfortunate they took the easy way out. It would have been so easy to have properly tested one listener.

[Mr. Widget]

That said, I image this upgraded external power supply would probably have distinguishable improvement on sound quality particularly because of all the digital components inside the chassis that are extremely sensitive to electromagnetic interference from the internal power supply. Also, I'd imagine the outboard supply has more and probably higher quality filter capacitance and regulation.

I agree with your logic and two years ago would have probably agreed 100%.

Decades ago I was shocked when talking with Don McRitchie on the phone when he told me that he ascribed to the Julian Hirsch school of thought which states that there is no audible difference between most properly functioning electronics with low measurable distortion and noise. Like many of you, I had heard massive differences between my own Marantz, Yamaha, etc. amps/preamps etc. and my own Threshold, GAS etc. amps and preamps. My take away at the time was that Don was either deaf or hadn't heard enough gear that wasn't mid-fi.

Since the advent of digital I have heard it get better and better... I have compared $100 USB DACs and $20K flagship DACs and heard the expected improvements. I exchanged a standard 75Ω digital cable for one that cost north of a $1,000. I heard the improvement. I swapped out a state of the art analog preamp for a digital one and heard the sound stage collapse etc. None of these comparisons were voltage verified matched output level comparisons and none were blind or double blind. But my thinking was that the differences were so obvious, none of that bother would be worth the trouble.

Today I am skeptical of many of my own carefully made subjective observations and by extension those of others. As I have researched this topic more and more it does appear that the overwhelming majority of us have happily duped ourselves. The professional reviewers too. I have had conversations with famous and well regarded audio luminaries who range from true believers in all the hype to the skeptical. When asking the skeptics why they don't acknowledge the nonsense they admit it is not in their own professional interest to publicly denounce the popularly held belief that there is higher and higher audible performance as we move up the scale. In my research I have found numerous controlled experiments where there was no correlation between sighted reviews and double blind tests. Here is a link to a good overview: https://audioxpress.com/article/diff...hats-the-truth Link to an amplifier comparison starting on page 78:https://www.worldradiohistory.com/Ar...Review-1987-01 ...and a major listing of numerous historical tests and articles: http://djcarlst.provide.net/abx_peri.htm

Even something as radically unique sounding as a loudspeaker. Yes, loudspeakers DO sound different, but in blind comparisons even the professional loudspeaker designers failed to pick their own creations at statistically significant rates when trying to choose their speaker out of several choices.

Because of this research and contemplation, I have decided to conduct my own level matched (voltage verified) blind/double blind test. I have recently ordered a digital pre/pro that I intend to insert into my main system to see if I can hear the difference between my $25K Mark Levinson No 519 streamer/DAC and the streaming pre/pro. For the test I will be inviting some much younger ears over to participate because my hearing is measurably less extended in the high frequencies than it was a couple of decades ago when I first met some of you. (Virtually and actually) A larger sample size will also make the experiment more valid.

My plan is to set the pre/pro to flat and unity gain. I will use the pre/pro and the Mark Levinson each as Roon end points so they can both play the exact same content and see if we can reliably tell one from the other. I'll let you know what the results are. It will likely take place after the holidays.


Widget

[toddalin]

Will you be able to do an A/B/X?

[toddalin]

a double blind A/B/X test would have been simple and only taken a half an hour for 1 participant.

The power supply connects with two umbilical cords versus the wall plug and I don't see how this could have easily been done.

[Mr. Widget]

Will you be able to do an A/B/X?

Not sure exactly how I will manage the test. Initially I will probably have someone switch between A and B in a random order. A/B/X is a little more difficult to control the time between A/X and B/X with the equipment I will be using.

At this point the details are all TBD.


Widget

[rusty jefferson]

The power supply connects with two umbilical cords versus the wall plug and I don't see how this could have easily been done.

Sorry Todd, unless I'm missing something obvious it shouldn't take but a few seconds to power down the preamp, remove the cover for the outboard supply cord and plug it in and turn the preamp back on again. Compared to many A/B/X tests I've taken, this is quite simple. Often times equipment has to be removed from a rack for cabling to reach, and then each piece carefully voltage matched for each of the 16 tests even if it's the same piece multiple times in a row. That's the only way a listener whose moved outside the room after each choice doesn't gain any information about which piece of equipment may be in use. The actual listening to music generally doesn't take more than 30-60 seconds to make a selection. My experience is if I don't hear it within 30 seconds there's little chance I'll get the 12 of 16 correct selections needed to ensure it's not random. If using an A/B/X switching system you lose some transparency but it does go faster. Decisions are usually made within just a few seconds of listening to music.

...Because of this research and contemplation, I have decided to conduct my own level matched (voltage verified) blind/double blind test. I have recently ordered a digital pre/pro that I intend to insert into my main system to see if I can hear the difference between my $25K Mark Levinson No 519 streamer/DAC and the streaming pre/pro. For the test I will be inviting some much younger ears over to participate because my hearing is measurably less extended in the high frequencies than it was a couple of decades ago when I first met some of you. (Virtually and actually) A larger sample size will also make the experiment more valid....
Widget

Excellent idea, however group A/B or A/B/X testing isn't a great idea in audio. One, or perhaps 2 people sitting one in front of the other is best. The differences in these tests can be subtle and often are only caught if sitting in the listening position. Image height/width/depth or perhaps sound being 'stuck' on the speakers as opposed to good transparency where no sound can be heard coming from the speakers are often not audible if sitting off axis, or low level detail/spatial cues, etc.

I haven't done a moderated test since Covid but have one coming up this winter also. It is getting tougher these days to voltage match with so much equipment having stepped attenuation. The voltage does have to be exactly the same or listeners will pick up the difference in level and not necessarily differences in equipment.

[toddalin]

Sorry Todd, unless I'm missing something obvious it shouldn't take but a few seconds to power down the preamp, remove the cover for the outboard supply cord and plug it in and turn the preamp back on again.

Sorry, but that's not A/B/X. A/B/X has to be instantaneous and X must be random. And, it has to be instantaneous at any point in the track and repeatable time after time after time. It can be single blind, or double blind and must have level matching.

My design/build A/B/X box with both line level and/or speaker level matching. Concept on how to do "X" was totally my own. Had to think about that one for a while.

https://cimg4.ibsrv.net/gimg/www.cor...49d910c3ad.jpg

https://cimg7.ibsrv.net/gimg/www.cor...cf99d2aec3.jpg

[Ian Mackenzie]

Widget and I were having an interesting discussion of the merits of power cables and I told him that I could reduce electrical background noise by a few dB simply by rearranging the power cord to the surge protector. This is shown as the background electrical noise level on the Behringer RTA with a noise floor of -113 dB. Granted we are talking background electrical noise on the order of -100 dB and if you are sitting in a room at an ambient level of ~30 dBA, would you even be able to identify this change?

This month's Stereophile Magazine auditions the Naim preamp with a separate/or not power supply. The external power supply is shown to completly remove a/c power-related spuriae (sp?), but with the onboard power supply, these spuriae are down at -115 to -120dB. Yet, those performing the audition were able to tell there was a difference and overwhellingly preferred the remote power supply.

So what does this tell us???

What makes you believe you are making a valid statement?

Were you using the correct procedure for your claimed measurement?
Is your RTA the right tool for making such measurements?
Do you have a qualification or a known reputation to support make statements on the noise your talking about?

Unless you can validate these questions the thread is purely your conjecture. The opposing opinions based on unsubstantiated arguments are equally frivolous.

It reminds me of the claims made in the link below which are viewed by the industry as dribble. It’s likened to an amateur TV channel without a broadcast license. The same applies to the now YouTube influencers who say anything to earn income from Google because it’s not a licensed media format with the exception of copyright infringement.


https://www.audiosciencereview.com/forum/index.php

[rusty jefferson]

:-) Thanks, I'm familiar with the process of using an A/B/X switching box. In the Stereophile case there is no practical way to use one. The listener can evaluate 'A' and then 'B' and a moderator can use a random number generator to determine 'X'. The listener can at anytime reevaluate 'A' and/or 'B'. Nobody is going to be arrested because the power supply couldn't be instantaneously switched. There are no lives at stake here. If you require the use of an A/B/X switching box to call it a random A/B/X comparison, that's cool. I don't.

[toddalin]

:-) Thanks, I'm familiar with the process of using an A/B/X switching box. In the Stereophile case there is no practical way to use one. The listener can evaluate 'A' and then 'B' and a moderator can use a random number generator to determine 'X'. The listener can at anytime reevaluate 'A' and/or 'B'. Nobody is going to be arrested because the power supply couldn't be instantaneously switched. There are no lives at stake here. If you require the use of an A/B/X switching box to call it a random A/B/X comparison, that's cool. I don't.

I am currently evaluating the difference in sound when using a 4.7 mfd Audyn cap on the Heil as opposed to using an oil can, 1,500 volt Dublier, 4 mfd (reads on the money) with a ClarityCap 0.67 mfd piggybacked on this.

I can instantaneously A/B the difference from my seating position and can hear a difference when switching back and forth..., but not on all cuts. Some are more obvious. If I had to wait for even a couple seconds, this slight difference would be lost.

Oh, BTW, the Audyns are sharper with maybe more detail, but edgier with more glare/hash. On some tracks they "shine" in respect to the Dublier, but can also "outshine" them..., and not necessarily in a good way.