Nobody spotted my mistake: inner radius is typically 0.06m, not 0.1m, so phase distortion is about 1/30th of a wavelength at 20kHz, not 1/50th. Still a fairly minor effect. Perhaps a digital guru could tell us whether it's even resoluble by the CD specification.
CD has a time resolution of approx. 600 picoseconds, which is 0.0000000006 seconds. Even if we allow your initial estimate, 20,000 Hz and 1/50 of a wavelength covers a time period of 0.000001 seconds.
So, 0.000001 / 0.0000000006 shows that CD is 1666.67 times more accurate than is required to show up the ultimate limitations of vinyl, in this regard.
It's in the detail of the Nyquist-Shannon sampling theorem.
Basically CD has a theoretical temporal resolution of 1/ (sampling frequency x no of samples)
Or 1/(44100 x 2^16) = 1/3.46x10^-10 or 289pS.
OK - thanks - understand now. Large trends very accurately resolved.
I'm sorry but I obviously did not make myself clear. I agree entirely with what you say. I gave those figures only so that we can dismiss this factor (offset variation) as a reason for increased bias at the inner grooves.Thanks for this, but I'm not yet convinced by either of these suggestions. I confirm that the variation for a 3 degree delta is about 13% (e.g. sin(20)/sin(23) ~= 0.87) but don't forget that this delta IS BETWEEN TRACK 1 AND TRACK 3, NOT TRACK 1 AND TRACK 5. You can verify this here:
http://www.sme.ltd.uk/content/Series-M212R-1536.shtml
If this is the cause of a need for variable anti-skating force, then the anti-skating force should increase as far as the middle of track three, peak there, and thence decline towards the last groove. I may be wrong, but that does not appear to be how the Caliburn Cobra is set up.
Again, I have to agree, but how else to explain the increase in bias (if it's real)?This is very counter-intuitive as well. The frequency does not change due to a slowing speed, so why should tighter wiggles matter. The stylus has correspondingly more time to navigate them, so the stylus doesn't really experience tighter wiggles. Think of fluid flowing through a more sharply bending pipe, but more slowly. The stylus sees the same snare drum frequencies it saw in the first groove and it navigates the same number of peaks of the same amplitude in the same time period. Assuming the energy transfer to the stylus is the same in each situation, why should drag increase? (BTW, fluid flow is a bad analogy because viscosity and turbulence mean that the pipe example is more acutely affected by speed, and there certainly would be less drag with a slower fluid in sharper bends. Turbulence within the fluid would wreak havoc with bend navigation.)
I did but ignored it because you were giving ball-park figures.Nobody spotted my mistake: inner radius is typically 0.06m, not 0.1m, so phase distortion is about 1/30th of a wavelength at 20kHz, not 1/50th. Still a fairly minor effect. Perhaps a digital guru could tell us whether it's even resoluble by the CD specification.
I always found sibilance a real annoyance until I started spending a lot more on TT-arm-cartridge. Maybe it was just that the cartridge had a better stylus and the setup was more precise?The only one applicable to a Rega arm, but most importantly a cartridge with a Micro Ridge profile.
Think of it this way (sorry if I'm being too simplistic).
The effective diameter of the record is reducing as the stylus moves across the disc surface. Assuming the same material is being recorded there is a 'bunching' and squashing of the undulations that form the analogue signal into a tighter space, making it harder for the stylus to trace them. In the orange/corner example above, imagine the corner as a more acute angle - you get an even worse fit.
You could get around this problem by driving the disc past the stylus at constant velocity (think how the speed of a CD varies as the laser moves across the disc).
Tips with a small minor radius cope far better with this effect and it dominates HF distortion, more so than arm geometry so long as this isn't badly off.
Best test (other than measuring which shows this all too clearly) is to play a vocal with strong sibilance at EOS. Horrid with many cartridges compared to the outer grooves, and of course digital. Doesn't bother some people but it drives me nuts.
I agree. Where does the 600 picosecond number come from?I don't understand this. How can CD resolve picosecond scale data when the sample period is 23 microseconds? Equally, with a frequency brick wall at 22kHz, if it can resolve a slight phase shift at 20kHz then it can only do so by the skin of its teeth. My experience tells me that cymbals invariably sound very slightly tinny and suffocated on CD or streamed 44.1, and I can't discern a 16kHz sine wave, so I suspect that redbook artefacts extend well below 20kHz. Can anyone produce more convincing numbers for redbook 20kHz phase resolution?
Just to clarify my skepticism, it seems to me that you are claiming that CD can resolve tones in the GigaHertz range. Impressive technology.
Is this right? 2^16 samples, not 2^16 levels for each sample?It's in the detail of the Nyquist-Shannon sampling theorem.
Basically CD has a theoretical temporal resolution of 1/ (sampling frequency x no of samples)
Or 1/(44100 x 2^16) = 1/3.46x10^-10 or 289pS.
I guess we'll just have to agree to differ, but I'll leave you with a few recommendations that I hope you might consider.
http://www.amazon.co.uk/Uchida-plays-Schubert-Mitsuko/dp/B000654OUG/ref=sr_1_7?s=music&ie=UTF8&qid=1299672614&sr=1-7
Basil, I'm going to veer off topic to ask you about this Uchida Schubert boxed set. All I have of Schubert's piano music is the Jeno Jando cd of the Impromptus on Naxos and I've never really liked it; I find it a bit heavy handed and stolid really, but perhaps that's too harsh. I love Uchida's Mozart - do you think her refinement and subtlelty will convert me to Schubert's piano?
Sorry to interrupt the row; please continue.
Do they play records in hell and cd's in heaven, or the other way round? If they exist you can all carry on the debate FOR ETERNITY!!
Actually Basil I've already started listening to them on Spotify and got so quickly involved that I did a rash one-click order of the set. The emotional arcs she creates are extraordinary - wonderful stuff. And I can't wait to hear them in full resolution. I'm really loving the way the Harbeths reproduce good piano recordings.
Many thanks for the tip!
I assure you you are not mentally distorting. What you stated, can be explained.Gosh ! I think I'm mentally distorting after reading that. I don't dispute the physics, but bite-sized sentences may have eased my aged brain in grappling with it.
WHY is tracking force higher on the inner groove wall when one might think that outward pressure would prevail? I know you're right, but why?
Does the fact that the arm is pivoted outside the circumference of the record have any bearing on this?
If bias should increase with playing weight, why do Koetsu cart's much prefer little or no anti-skating when, say, a Lyra playing at .25 of a gramme lower performs better with a much higher bias?
8 track tapes- Called a method of pulling toilet paper out of the cardboard center and then rewinding it back on again...on the outer layer.Tony,
No 8-track? What do you use to listen to your truckin' hits?
Joe