Comment on Audio cable measurements are driving me crazy — why don’t they null?!?
dsilverz@calckey.world 1 day ago
@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.
Uebercomplicated@lemmy.ml 1 day ago
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
dsilverz@calckey.world 19 hours ago
@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.
Uebercomplicated@lemmy.ml 12 hours ago
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!