- cross-posted to:
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- cross-posted to:
- [email protected]
cross-posted from: https://lemmy.ml/post/43120463
TLDR (I’m very long-winded): this YT video took measurements of three different audio cables, including a 200€ one, and found differences where there should be none. My physics knowledge (and general consensus among the scientific community) says the measurements of the different cables should be identical or near-identical — or I am, at least, under that impression. My own measurements, because the channel does provide the files, confirm that the expensive 200€ cable does measure differently from the others. But surely something else must be causing this? Please help me find out what that is, Lemmy!
Edit: see this and this other excellent comment.
Below, I go into a little more detail and context, and I go through what I have tried, etc.; I tried splitting everything up into chunks to make it easier to read, but I was never good at being succinct. Sorry about that 😬 :P
Context: What Am I Talking About?
Firstly, I should clarify that this isn’t relevant to most people, only really physics and audio-technology nerds. But I’m desperate. This question has been tormenting me for days…
I should provide some context. For some reason, YouTube gave me a rather odd video suggestion. I am very interested in audio technology, mixing, and mastering, but I’m not a snake-oil audiophile type. I guess you could call me a lover-of-audio, e.g., audiophile, but I don’t attach myself to that community. So you can imagine my confusion when this video was suggested to me on YouTube.
For anyone unwilling to click on an ambiguous YT link like that, here is a brief description: audiophile guy (who believes that cables affect sound) compares three cables, two of which are “cheap” (e.g., approx. 50€) and one of which is expensive (like 200€ — for a cable). His conclusion is ultimately (yes, I watched that far) that they don’t really affect sound, because they’re just interconnects (so RCA cables), and not speaker or power cables. But he actually records each cable and provides those music files — which means I can compare them as well…
By “records each cable,” I mean that he used each cable to connect a CD-player to a pre-amp (for some reason) and then an analogue-to-digital convert (ADC) into his computer, where he can record the output; this way he gets just the supposed difference the cables make. I realize that the CD-player might have some inconsistencies, since CDs are a moving medium, but jitter compensation and stuff like that is very advanced these days, so this is getting pretty close to an accurate measurement of the cables, I think (correct me if I’m wrong!).
In the video, this guys claims that the measurements show a difference between the cables. This debate around cables is something I thought was quite contested, so I naturally decided to download the tracks (which he provides in the description) and compare them myself. Here’s what happened.
My Own Testing: They Don’t Null
So I downloaded his recordings, phase-aligned (which they weren’t already) everything and normalized to peak (which, again, was necessary, and creates the lowest delta compared to LUFS, etc.), and then null-tested. That means I inverted the phase of one, played two of the files at the same time, and thus got the delta between them.
The Mogami and Belden cables (the cheap ones) are nearly identical; there is a slight difference in the null-test, but it is statistically small enough, that I attribute it to measurement inconsistency (e.g., CD-player, DAC, or ADC performance, but also maybe natural conditions, etc.). I especially suspect — given that most differences occur at higher frequencies but aren’t really audible when listening — a jitter related issue, causing the timing to be just a little off, thus creating a delta in the higher frequencies. This could be due to the CD-player, but I have no idea.
…the Neotech (the expensive one), however, is significantly different.
Firstly, he provides the file for the Neotech cable with a significant phase delay compared to the others, of about 50 ms, and it is also about 0.02 db louder than the others. That is rather suspicious on his part. This alone makes it sound better, but when I correct this volume and phase difference — it still sounds better, and the null-test confirms that it is still quite different (we’re talking differences up to -40 db here, which should definitely be audible).
It turns out, the volume difference actually changes throughout the song; meaning that in some places the difference is 0.01 db, and in others 0.03 db. But I can correct for that! I don’t know why it happens (someone smarter than me, please explain), but I can correct for it… And yet, the null test still shows a clear difference (especially when the singer makes s-sounds, i.e., sibilance).
Please Help Me
What is going on? My physics knowledge tells me this should be impossible.
I can only imagine that for some reason the Neotech is more conductive, or something like that, and therefore recreates the harsh and very fast dynamics of sibilance more accurately.(edit: crossed out because this is a little too ridiculous) But the difference in conductivity should not be enough to cause that… I really am confused. Someone with more expertise please explain this!For context, I cannot blind test ABX the Neotech. (edit: meaning, I cannot hear any difference whatsoever.) This is very subtle stuff here. But I can see a difference, the null test shows differences as high as -45 db when the singer does those s-sounds and everything has been normalized. So clearly something is happening (and again, this is phase aligned and normalized and everything). So what could it possibly be?
Edit: here, for clarity, screenshots of the null test at different moments in the tracks from the youtube vid (here nulling between the magomi and neotech).
Normal part of song, no sibilance or cymbals, but otherwise singing, piano, bass guitar, drums, etc.:
When the singer creates sibilance with an s-sound:
The null test was performed in the Reaper DAW with Voxengo SPAM and Reaper’s built-in phase align, normalization, and phase inversion.
Lemmy, please show me what I have missed! Show me the obvious error I or the video creator made. Sorry to make such a long post on c/asklemmy, but I don’t know where else to ask.
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Maybe you’ve heard about a page called Audio Science Review. The owner amirm did some tests with a much more sane setup which he describes in detail. He actually finds his high priced cable (well above 2000 USD in this case) to perform worse than the cheap ones if anything, picking up more noise. I will trust his objective measurements any time of the day, this guy actually knows what he’s doing.
Adding to this, as I have now skimmed over the original video in question by ANA[DIA]LOG: He already introduces the topic by clearly stating that he is strongly biased towards “cables make a difference”, I can only assume he lacks the necessary fundamentals about what a cable does. He describes his test track to have “a lot of frequencies”. We don’t know about the gear he used, and he chose a singular test which cant’ be replicated as it has too many muddying variables. The data he shared had to be sanitized by you, to even give any chance of an objective interpretation, which really is impossible in these circumstances. When his test shows some differences, rather than being surprised and questioning the sanity of his test-setup, he just accepts the result that satisfies his bias. This is not science, this is a grifter trying to sell snake oil to the gullible.
Yeah, you’re right. I should have just stopped when he said his source was a CD player, meaning he had no pure digital copy (i.e., no control) to compare too. Or, at least, he didn’t provide one… I get hung up on things easily. Thanks, though, you’re 100% right
I love ASR and am a long time reader of Amir’s reviews and measurements :). I am more curious, in this case, about what, since it’s probably not the cables themselves, is creating that delta in the null test. That’s the part I can’t figure out, though I’ve pretty much resigned myself to just presuming it’s something else in the YouTuber’s signal chain and calling it a day.
Yeah I don’t think there is anything of value to be found here. I added another comment highlighting the problems I see with this test here.
bookmarked 2 weeks ago:
Audiophiles Can’t Differentiate Audio Signals Sent Through Copper, Banana, and Mud in Blind Test
I saw this back then as well :P and, you’re right, it holds true here as well. As I say towards the end of my rather lengthy post:
For context, I cannot blind test ABX the Neotech.
I can’t hear the difference! But it bothers me so much that I can see the difference on the graph
Ok, assuming you are posting this honestly instead of just pushing something…
Take a look on the meaning of “noise”, and how much of it your devices create. The best description of what is happening in your entire text is “nothing”.
Thank you! I don’t know the YouTuber’s gear’s noise floor, so I don’t know how much of an influence that should be having, but I would presume quite low. But I’m not entirely sure if I understand what you mean. The null-test I did (I’ll attach a screenshot to this comment) mostly showed a delta in higher frequencies, specifically when the singer makes sibilant sounds. Does the graph look like what you would expect from system noise?
Null test while the singer is making a sibilant sound (via Voxengo SPAN and Reaper):
Null test while the singer is not making any sibilant sounds and the cymbals aren’t playing:
Thank you for taking me as good faith. I realize now that my post-title sounds a little click-baity, like I’m suggesting that there’s an authentic delta in the null test. I very much don’t think that’s the case; I’m just trying to figure out what a plausible reason might be, for why I’m measuring a delta in the first place.
I guess ei incumbit probatio… the burden of proof lies upon the YouTuber here, so I shouldn’t get too worked up about this :)
Your graph has a signal of -40dB. Are you working in high-energy physics? If it’s only nano-tech or something of this magnitude, you don’t have equipment that is this precise.
And all the “high-intensity” findings on your posting (at audible 0dB) are probably because the expensive cable didn’t connect well to the socket. And are still nothing, and have no impact on your sound quality.
I realize I may have left out something key to understanding dBFS for the unfamiliar. Unlike with dB SPL, which is what you are referring to with “at audible 0dB,” zero dB refers to the loudest possible sound in dBFS. The unit stands for decibel relative to full scale, where full scale (loudest possible sound) is 0 dB. So in dBFS, unlike with dB SPL (sound pressure level), all audible sound is stored as a negative dB value. When you listen to the audio file, this is first converted to a voltage, and then to sound pressure, which is finally measured in positive dB SPL.
If that doesn’t explain it for you, I don’t know what you don’t understand, and I can’t help. I would recommend finding some YouTube videos on the subject, in case you’re a visual learner.
I’m not sure if you’re reading the graph correctly, this is the delta between two of the digital files from the video’s description. So a signal of -40 dBFS is quite audible, since it’s all relative to 0 dBFS (full scale).
And it isn’t the recording itself, it’s just the difference between two of the recordings provided in the video’s description. This is commonly known as a digital null-test, and let’s you find the amount (and significance) of difference between two digitally encoded recordings, and in particular at which frequencies those differences lie.
You can try doing it yourself by downloading the audio from the YouTube video’s description and then playing two of them at the same time in audacity, but with the phase inverterted for one of them. Just make sure the phase and volume are aligned. Then you can hear the difference between the recordings yourself!
The question is, where does this difference come from.
So a signal of -40 dBFS is quite audible, since it’s all relative to 0 dBFS (full scale).
At -40, it doesn’t make any difference what kind of dB you are talking about.
(Well, if you are looking for superstrings evidence or even quantum gravity, it does, but I guess it’s not your case.)
It sounds like you think -40dB is such a small factor it must be inaudible. It absolutely is audible, the ear has like 100dB of dynamic range
Relevant line:
US installations use +24 dBu for 0 dBFS
That means the US definition you can’t hear anything below -24 dBFS. It’s the largest value there, it’s -18 for the EU.
BTW, you also seem to have misunderstood dBU. That is in voltage, which means the signal is amplified before you listen to it. I would highly recommend reading the wiki page on decibels: https://en.wikipedia.org/wiki/Decibel
I think there’s good YouTube videos on how decibels and digital audio work as well.
What you quote is for conversion with analog levels, which is not what’s happening here. Everything I’m doing is 24 bit digital audio, which has 144 dB of dynamic range. That is a little over-kill, which is why most audio files are distributed as 16 bit, so 96 dB. That means you can hear anything from 0 dBFS to -96 dBFS (with proper dithering). That is why the cutoff point in the graphs I showed you is -100 dBFS, since you realistically won’t be able to hear below that anyway (audiophiles disagree), in the final file.
-40 dBFS only represents how the signal is stored in the digital file. It has nothing to do with the signal’s actual volume. I play those -40 dbFS through my computer, then my DAC, which outputs at about 2 VRMS, into my pre-amp, which increases the voltage again, into my amp (which, again, increases the volume), and finally into my speakers, which output that -40 dBFS, which is now signal at about 70 dB SPL (actual volume).
Edit: just checking now, and my DAC converts -40 dBFS to about 0.02 volts RMS. With no additional amplification, that outputs roughly 80 dB SPL on my earbuds. But you would usually add additional amplification.
dBU is for analog line-level, and the conversion you showed is what I would use when routing my console back into my computer. But analog line levels are still very audible at -40 dBU, usually, not that that’s relevant.
You have to understand that this is not real volume. It is just how the volume is stored digitally. If you have a -40 dBFS noise floor in your audio file, and the music has a 12 dB dynamic range peaking at -1 dBFS, you will hear the noise clearly throughout the entire track, because you are amplifying the entire thing greatly, since you are ultimately transforming this into dB SPL.
Here’s a simple answer: cables going from analog input devices to DSPs, mixers, etc. need proper shielding and should be as short as possible, with low-resistance connectors. Otherwise, EM radiation can be picked up and interfere with the signal.
Anything traveling digitally? It just needs to arrive at the destination in a timely manner; your cable would have to be really bad to have any influence.
Cables out to analog speakers? As long as you have a decent signal, these can use the crappiest connections and unshielded cables — the worst thing they’ll do is provide interference for OTHER cables they’re near. Just adjust your EQ until the speakers provide the response you’re looking for.
cables going from analog input devices to DSPs, mixers, etc. need proper shielding and should be as short as possible, with low-resistance connectors.
Are balanced cables applicable here; they would remove any noise, right?
As for everything else, I 100% agree. If I can’t hear the difference, then I don’t care :P honestly, the only cable that I’ve found to be important is for IEMs, since you want to avoid microphonics there. Apart from that, anything that won’t cause a ground-loop is perfectly fine.
I’d say it’s too hard to tell without buying the cables yourselves and verifying the results instead of trusting the youtuber’s files. I’d also use a different source to rule out the cd related issues if you could. I can understand why you wouldn’t want to drop $300 on something so grossly unimportant though.
This is it, thank you. I have never even seen a cable that expensive in person, and I’m certainly never going to buy one. I don’t know why this YT video triggered me so much, especially given that there’s no way to verify what that guy is saying he did is actually accurate.
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I’m not an audiophile, but I’m someone who has some practical tinkering with amateur radio. It may seem like a whole different field, but both fields more or less share similar concepts and situations, especially when it comes to audio cabling. High-end cables and equipment (not in the “pricey” sense: although high-quality materials will make the thing costier, high-priced don’t necessarily mean high-quality, sometimes a high price can be disguising a low quality “cut-costing” material) can indeed lead to measurable differences. There are real problems such as EMI, self-induced EMI (the circuitry inside the audio equipment generating its own EMI like an Ouroboros), poorly-grounded shielding, switched-mode power supplies’ “dirty” current, among other problems that may or may not appear when analog is being used somewhere (especially the ADC that you mentioned) depending on the quality and other factors.
The audio cable, itself, can end up acting as an antenna, roughly similarly to how the “FM radio” function on many smartphones work by using a plugged wired earpiece (the earpiece cable becomes a FM broadcast receiver antenna, which wouldn’t fit inside the phone depending on its form factor). Good cables will have a proper shielding acting as close as a Faraday Cage as possible, while also dealing with cable capacitance (a problem in itself when dealing with different frequencies such as in audio situations; it’s likely to do with the measured differences across the audible spectrum)
Again, I’m not exactly knowledgeable about professional audio equipment, but some of the principles seen when dealing with radio transceivers may apply because, deep inside, they share the same laws of physics.
What you say is very interesting, but I am starting to suspect that it really is just inconsistency with some other component. The delta isn’t consistent like it would be (I think) with ordinary noise or interference. It’s that weird delta between 2k Hz and 15k Hz that I can’t explain. The YouTuber is also a rather odd in that he doesn’t reveal what pre-amp he’s using, which in the case of taking measurements, is all the more suspicious. I don’t know, I think I need to stop thinking about this. Maybe you’re onto something, and some computer part was creating noise at that frequency range right when that cable was being measured.
The problem is, though, that I will never know, because I’m relying on a random YouTuber’s opaque recordings. And I’m not about to buy cables in that price range to test myself. Thank you for your expertise, though! I’ve always wanted to get into radio, but it has seemed awfully complicated and rather expensive
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What you say is very interesting, but I am starting to suspect that it really is just inconsistency with some other component.
If the only varying element across the tests is the cable, everything else unchanged, other components wouldn’t have a reason to behave differently, except as a consequence of properties/factors modified/added by the cable, such as capacitance, length (thus, electrical resistance) and whether it ends up resonating more with some nearby EM source (be it a nearby radio broadcast station and/or air traffic, or interference emerging from household equipment, even HDMI creates interference as, for example, I myself manage to capture Van Eck Phreaking from my HDMI display using a UV-5R up to a few dozen meters away).
The delta isn’t consistent like it would be (I think) with ordinary noise or interference. It’s that weird delta between 2k Hz and 15k Hz
Noise doesn’t always behave uniformly across a spectrum, sometimes it’s more pronounced for specific frequencies, especially when carriers are involved (carriers as in AM/FM carrier, the primary wave centered at the channel’s given frequency, e.g. a 120MHz AM QSO between a TWR and an aircraft happens with a signal centered on 120MHz whose amplitude is modified by an input signal (the mic audio from pilot/ATC operator), thus the “AM” amplitude modulation). The freqs where an EMI is more pronounced are often its “harmonics” (freq subdivisions).
But this specific range you mention, it also sounds like power supplies. It’s quite the range expected for EMI. While nearby power supply weren’t changed, one cable might be presenting physical properties which allows it to better resonate with the EMI emitted from those, likely the cheaper one (the high-end cable theoretically have better shielding so it’s less prone to resonate with EMI as a cheaper cable would).
creating noise at that frequency range right when that cable was being measured
Or, as I mentioned above, the cheaper cable might be resonating more with some constant source of EMI, be it from within PC or something nearby (even household appliances).
Thank you for your expertise
I’m far from being an expert myself, I still got a lot to learn, but thanks for the compliment!
I’ve always wanted to get into radio, but it has seemed awfully complicated and rather expensive
I’m more into listening (RX) than transmitting (TX), I don’t even have a QRA for TXing QSOs myself. Even though I got a transceiver (a Baofeng UV-5R), I use it only for RX at nearby VHF and UHF stations, together with a RTL-SDR, both of which are pretty cheap. Reception (“owling”, “to owl”, to observe as owls do, only listening to the QSOs) is even more sensitive to EMI (this is how, for example, I found out my HDMI spills out lots of EMI), so that’s why cable quality ends up being sine qua non for radio listening, too.
So, ironically, the expensive $200 cable he compliments to greatly might actually have the worst shielding. This just goes to show that the only way to approach this is scientifically, and that the YouTuber’s very unqualified self shouldn’t be performing these tests with any authority!
Quality Control is what you’re paying for…
For pretty much any type of product where quality shouldn’t matter you can buy cheap, normal, expensive, insane.
100/1000 of cheap ones might have sleight flaws.
10/1000 normal may have flaws.
1/1000 expensive
And 1/100,000 for the insanely expensive ones may have a flaw.
So even if their optimal performanceshould be the same, the more expensive it is, the less likely the manufacturer lets subpar products out to market. Often it’s vertically integrated and as batches fail they get bumped down to a different label
Do the test again, they might score the same. But do it enough, and you’ll see the expensive ones eventually pull out ahead by a very sleight amount
![[Resolved] Audio cable measurements are driving me crazy — why don’t they null?!?](https://lemmy.ml/pictrs/image/d6d243aa-57fd-4bb9-8fe6-1d298fac7152.jpeg){kind=link}