Popular Post Superdad Posted October 12, 2019 Popular Post Share Posted October 12, 2019 2 hours ago, gmgraves said: USB cables? As far as I’m concerned, they have even less chance of being able to alter the sound, because the digital data is either there or it isn’t. Of course, that’s a matter of indifference to me because I think all USB is compromised as a digital audio transmission medium and sounds terrible. Hey George: How can both those statements be true at the same time? Teresa, sandyk, barrows and 4 others 5 1 1 UpTone Audio LLC Link to comment
Popular Post Superdad Posted October 13, 2019 Popular Post Share Posted October 13, 2019 16 hours ago, gmgraves said: I suspect that if, indeed, USB cables alter the sound when the received data is unaltered, then either different cables “smear” that data enough to cause audible errors, or, it’s another case of listener bias. You do know that what travels on a USB is not "ones" and "zeros" data, right? It is very high-frequency "analog" DC voltage, and inside that "noise," every 125 microSeconds comes a modulated packet in which the data is encoded. Then, in every USB input--be it a printer or a DAC--is a PHY chip (these days integrated in the USB MAC processors, but its function is there nonetheless) whose job it is to determine what in that bursty/noisy high-speed signal is a "one" or a "zero." Study the function of a PHY for a bit (@JohnSwenson has actually designed PHY chips) and you will see they are filled with PLLs, clocking at various phases, and funky gain circuits to allow them to decode some rather piss-poor signals. The harder the PHY chip has to work, the more noise (from bursty current demand) it puts on the ground plane--inside the DAC. And this is measurable inside the DAC. This brings us back to the reason USB cables can "sound" different (as well as the raison d'être of our REGENs): Impedance match and signal integrity. This is measured on an eye-pattern, which will show amplitude, slew, noise, and jitter. And while yes, anything within the USB spec will allow the PHY to do its job, for audio it is bit like with other measurements. That is, the measurement folks will say that below a certain threshold we can not hear differences of distortion, jitter, slew rate, transients, etc.--yet people hear plenty of differences, some of which probably have no correlation to present measurements. So I don't care how good someone is at interpreting an eye pattern: it's just proving there are differences between the cables or the signal--it can not be used to characterize what will be heard. So George, I question you when you say "All USB audio is equally poor"--while at the same time saying that all USB cables sound the same--because it demonstrates either your lack of technical understanding or a lack or curiosity. feelingears, numlog, Sonic77 and 10 others 8 1 2 2 UpTone Audio LLC Link to comment
Superdad Posted October 14, 2019 Share Posted October 14, 2019 4 hours ago, mansr said: Can you explain this concept of "high-frequency DC" a bit more? Of course I was referring to the data rate. But you knew that... UpTone Audio LLC Link to comment
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