Re: Vynil or digital?
Reply #111 – 2017-07-07 02:50:39
... See above. The rule of thumb being that phase shift can be measured to about 1/10th the cutoff frequency; from this we can see that no current audio recording system has wide enough bandwidth- yet. This is basic filter theory and is why amps and preamps have had 100KHz bandwidth going back to the 1950s. You may wish to qualify that. You're only right for some simple cases of second-order filter response. ... You don't need state of the art to get 40KHz bandwidth- nearly any modern era LP pickup can do that with ease. They can probably go higher but most cutter electronics are bandwidth limited (ours are limited to 42KHz) to prevent stability issues so the recordings needed for such proof can't be made without special consideration. I've not seen the need for that so far. By your reasoning quoted above, the phase shift of your cutter therefore goes increasingly bad above 4 KHz. Pinch Effect- That's actually funny! This statement is blatantly false and clearly made without measurements or hands-on experience. That's the sort of thing in which subjectivists engage! Some here are probably to young to recall, but RCA marketed color video recordings on vinyl, played back with a stylus. Again my recommendation is to work with a lathe rather than engaging in myth and rumor. As I pointed out in my remarks earlier, I had many of these same false impressions until working with the real thing set me straight. Pinch effect is quite real, though sometimes overstated. As for RCA's recordings, they bore almost no resemblance to what you do. There were two competing systems. Both used FM modulated carriers. One system used a vertically modulated groove tracked with a strain-gauge stylus . The other used a system of alternating pits and lands similar to CD (but larger) tracked with a capacitive sensing stylus. Both systems suffered from premature stylus and disc wear problems. I also have photomicrographs of CD-4 grooves after a dozen or so plays with the correct cartridge and stylus profile, showing the carrier almost completely worn off the part of the groove contacted by the stylus.