Originally Posted by tomelex
If the power bandwidth of your source is down 3db (per octave) at 15Khz and the power bandwidth of your playback is down 3db (per octave) at 15Khz what have you lost?
If the same source as above, but your playback bandwidth is down 3db at 20Khz, what have you gained besides noise?
Maybe you could elaborate on what you mean here.
I would disagree that analog really has more bandwidth than digital......
Sure, a really well recorded LP can theoretically have SOME information up to 40 kHz or so, but there's more to it than that. First, let's remember that RIAA curve - where the high frequencies are boosted... Don't try and get a 20 Khz cymbal crash onto that record at 0 dB, or at -20 dB.... you'll overload something awful. If you don't overload the amps, you;'ll either melt the lathe cutter head, or bounce the needle right off the record. And, since you bring it up, exactly how much phase shift does that inductive electromagnetically-driven cutting lathe have? And how about the playback cartridge? To suggest that a record can reproduce ultrasonic frequencies with accurate phase and amplitude characteristics is rather a stretch.
Its pretty obvious that you have not spent a lot of time around a cutter. It has no problem doing 20KHz at 0VU, with no worries about frying the head
This is because 0VU is a walk in the park as far as the cutter is concerned. Now it is true that they are easy to fry as they don't handle a lot of power and the amps driving them always have a lot of reserve, usually some multiple of what the cutter can take. But by the time you fry the cutter, its making a lot more than '0VU' (in quotes as the level on an LP is a relative thing).
What is really important is what the cartridge can playback, which is a different topic altogether. They do have difficulty with that kind of level at that frequency. Fortunately stuff like that does not exist in actual recordings, so the argument *may* be a red herring. We've put 30KHz on lacquers and played it back on a pretty modest system, so I stick by the HF bandwidth claim. We've also cut 5hz tracks. Pretty interesting to see that it can go that low...
While we're on the subject, what exactly IS the phase-response of a microphone? How many degrees of phase shift at 10 kHz does a "good" microphone have? For that matter, what is the total THD of a cutting lathe + vinyl + cartridge + phono preamp signal chain? I'm betting it's nowhere near the 0.03% or so of a decent A/D and D/A.
Honestly, I've heard some very good vinyl systems, and some of them sound DIFFERENT than a good digital system, but I'm simply not convinced that they are BETTER - or more accurate, or lower noise, or lower distortion, or anything else *I* use as a metric of "sound quality".
The THD of the lathe by itself is pretty low, as the operation has so much headroom. But one thing it lacks entirely is the inharmonic distortion (a form of IM) which is something that all digital systems have to some degree. I don't see it as a spec in measurements though, my guess is because its embarassing. The ear interprets that kind of distortion as a brightness BTW.
I agree with you in basic principle - but I think you are overstating the claim.
First off, we DO have a defined maximum bandwidth - and that is the limit of human hearing. We don't have to consider 1.2 mHz noise because we can't hear it - so we can call our "bandwidth of interest" the limits of human hearing (even though we may disagree slightly at the precise numbers involved). Second, there are indeed different types of noise, with different characters. I would even "give you" that analog noise (in the form of white noise hiss) is relatively innocuous whereas at least some forms of digital noise (especially some data correlated types) sound quite discordant. So, I think we both probably agree that we would rather hear a nice smooth hiss noise floor at -70 dB than a ragged, jagged digital one at the same -70 dB.
BUT, that's not what we're comparing. What we're really comparing (when we compare a quiet vinyl pressing to a 24 bit digital recording) is a nice smooth -70 dB analog noise floor (if we're lucky) with a nasty, awful sounding digital noise floor at -130 dB. (If you play a 24 bit recording so the loudest points are approaching the noise level of a fighter jet taking off - and absolutely threatening your hearing - the noise floor will be somewhere below the sound of the blood rushing through the veins in your leg.)
Not all people are limited to 20KHz but more importantly its been shown that if you don't have 'excess' bandwidth in your equipment, it will not sound right on account of group delays (phase shift). That is why wide bandwidth in amps and preamps has been pushed by the more respected designers since the 1950s. IOW even though we humans can't hear over 20KHz, the effects of not having more bandwidth is audible. The engineering rule of thumb is 1/10th the cutoff frequency. In this regard analog fails, whereas digital fails miserably. They both need to exceed 100KHz at the very least...
FWIW -70 db is not by any means the noise floor of the LP. That might be close to what some tape formats do but the LP itself can be considerably quieter. Not sure exactly *how* quiet they are as there are so many variables, but I can tell you that the lacquers are pretty much dead silent- they must be the range of the mid to upper 80s. However when you press an LP the noise floor increases, although with a good pressing plant exceeding -70 db as a noise floor is easily done. We see that from RTI quite often. QRP (Acoustic Sounds) can do even better as their pressing machines are particularly still during the pressing process, resulting in a lower noise floor.
