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.
@Uebercomplicated@lemmy.ml @nostupidquestions@lemmy.world
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
@Uebercomplicated@lemmy.ml @nostupidquestions@lemmy.world
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).
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).
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).
I'm far from being an expert myself, I still got a lot to learn, but thanks for the compliment!
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!