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¿End-of-side distortion — inherent to vinyl?

Discussion in 'audio' started by Chris, Mar 8, 2011.

  1. sonddek

    sonddek pfm Member

    BTW, using measurements from this page:
    http://www.vinylengine.com/phpBB2/viewtopic.php?t=22894

    ...I reckon that a typical modern stylus generates an inner groove error of about 0.4 micron. Distance between mean points of contact: 24 microns
    Phase error: 24 microns x sin(1 degree) = 0.42 microns

    A 20kHz signal in the inner groove gives a wavelength of about 20 microns, calculated as follows:
    radius: ~0.1m
    groove speed: 2 * Pi * 0.1m * 100/180 = ~.35 m/s
    Divide by 20,000 for 20kHz wavelength = ~17 microns

    So the phase distortion is about .4/20 of a wavelength, i.e. 1/50th of a wavelength at 20kHz at the very innermost groove. And don't forget, this is only a phase mismatch at very high frequencies. Good luck hearing that.

    Across the great majority of the record it's much smaller or zero. This is probably why experienced enjoyers of affordable elliptical and better styluses are not complaining about this issue.
     
  2. Joe P

    Joe P certified Buffologist / mod

    John,

    That new classical vinyl at Acoustic Sounds, as nice as it is, is almost entirely of old performances. Try to find classical on vinyl from performances that were recorded in, say, 2010. Recent classical recordings on vinyl are almost non-existent.

    My point is just that if you care about music, not the format it's on or audiophilely things about which is superior, you can't limit yourself to a single format.

    Joe
     
  3. John

    John Fore!

    There are great performances of most classical repertoire on vinyl that can be had without too much effort to satisfy most but maybe the most rabid aficionado. I can live with the millions of choices available on vinyl despite not being considered a music lover.
     
  4. Joe P

    Joe P certified Buffologist / mod

    John,

    Would you feel any different if you couldn't buy any pop or rock recorded after 1989?

    Don't get me wrong. I like vinyl and when it's recorded, mastered and played back properly I prefer it to digital, but sticking with vinyl only is to unnecessarily limit your choices.

    I have bought some classical reissues and they are very good, but they're expensive and for the price of one audiophile LP I can get a 12-CD set of classical recordings at Amazon.

    (And now that downloaded tracks and rips of CDs are the things the masses do I'm finding that plenty of great used CDs are becoming available in the shops, just like the way LPs did when the Mescalitos discovered digital.)

    Joe
     
  5. kasperhauser

    kasperhauser pfm Member

    Important distinction though, from my perspective, is that if I couldn't get Pearl Jam's "Ten" (released in '91), I can't just settle for the version recorded by The Jam ten years earlier, as Weller and Co. never recorded any versions of "Jeremy" or "Evenflow" that I'm aware of. However, while I may not be able to get Tintner's 1999 release of Bruckner's 9th, I can possibly content myself with Bruno Walters' 1959 version, and still get a lot of enjoyment.
     
  6. John

    John Fore!

    That's my take as well.

    One doesn't need to limit oneself to reissued Classical vinyl, there's tons of cheap vinyl out there in mint condition if you make the effort to find it. Most estates practically give it away!
     
  7. Nik

    Nik pfm Member

    As you have correctly said several times, bias (torque) is caused by the stylus drag (force) acting on a line that does not pass through the arm pivot. Its magnitude is given by multiplying the force by the distance of its line of action from the pivot.

    The distance varies with the sine of the actual offset angle and is greatest at the outer and inner grooves and least about halfway between. For a 9" arm this variation is about 13%.

    It seems that the force doesn't vary with speed but varies inversely with wavelength. As we get nearer the centre of the record the wavelength reduces so the wiggles get tighter and tighter and the drag increases (think of fluid running through a pipe with sharp bends in it compared with a pipe with bends of the same amplitude but much more "stretched out": which gives the most resistance?).
     
  8. Tony L

    Tony L Administrator

    Agree completely - an audio system is merely a tool to replay recorded music, IMO that means it should be able to replay any format that contains music that interests you. I can play shellac, vinyl (at all speeds), cassette tape, CD, SACD, VHS, DVD and pretty much any computer audio format. I'd hate to lose the ability to listen to any of these, though I'd have to go down to the basement to retrieve my VHS player and cassette deck!

    Tony.
     
  9. kasperhauser

    kasperhauser pfm Member

    I still have a couple of wire recordings I got from my dad. Sadly, the recorder itself died long ago.
     
  10. Joe P

    Joe P certified Buffologist / mod

    Tony,

    No 8-track? What do you use to listen to your truckin' hits?

    Joe
     
  11. sonddek

    sonddek pfm Member

    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.

    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.)
     
  12. sonddek

    sonddek pfm Member

    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.
     
  13. Robert

    Robert Tapehead

    EOS/tracing distortion till exists to some degree with all stylus profiles, in all arms and with all geometries. The only way to eliminate this is to use a replica cutter profile to play the vinyl and a parallel tracking arm. The former is not practical as you'd cut and damage the vinyl.
    Minimising end of side distortion therefore requires a stylus profile with a very fine minor radius - somewhere between 2.5-4um.
    This excludes nearly all ellipticals and certainly all conical tips. Many Line Contact tips are also excluded as the radius is still too large, typically 6-8um. Line just means that the footprint extends further down the groove wall and that doesn't make them any better at tracing very tiny HF undulations on the groove wall, though it can give more secure tracking (a slightly different thing) and reduce record wear.
    This pretty much means you need a MR, VDH, Gyger S and a handful of other cartridge manufacturer branded profiles. MR has certain advantages as the scanning surface maintains shape as the tip wears. All others progressively 'blunt' the scanning surface from day one of use.

    EOS and tracing distortion is probably the thing I dislike most about vinyl and always have.
    Most cartridges have far too much.

    For a practical example, take a large orange and a small egg. The orange represents a standard conical tip and the narrow end of the egg is our fine MR/VDH type tip.
    The 45 deg corner in your room represents the HF signal on the groove wall.
    Offer both the orange and egg up into the corner and note how tightly each one fits the angle.
    There you have the difference between a standard and a fine profile tip. The snugger the fit into the corner, the lower the distortion.
     
  14. sq225917

    sq225917 Bit of this, bit of that

    So what alignment did you use on your Rega then to minimize this huge effect?
     
  15. Robert

    Robert Tapehead

    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.
     
  16. sonddek

    sonddek pfm Member

    Fluff.
     
  17. Joe P

    Joe P certified Buffologist / mod

    kasp,

    I agree it's not entirely comparable — a great performance of Beethoven's ninth from 1956 may be the only version you'll ever want or need — but it always comes back to the same point for me: I can't get every new release I want on vinyl, just as I can't get every recording ever pressed on vinyl as a CD.

    I fully understand format preference — and I'm more than thrilled that vinyl continues to live — but I don't get purposely limiting yourself to a single format. That's like saying you'll only watch films that were shot on Ektachrome or something.

    Joe
     
  18. Craig B

    Craig B Re:trophile

    My turntable has been operating under the impression that groove velocity remains a constant across the whole of a record side.

    Naturally, my pivotal tonearm is aware of its tendency to wear its tip on the left and, therefore, provides a constant outward lateral force equal to that of downforce.

    Of course, my cartridge knows full well that a skinny one will fit and follow the increasingly tighter turns better than a fatty will.

    Record players are smart like that.

    Craig
     
  19. MartinC

    MartinC pfm Member

    Barry,

    Can't say I agree. Comparing my LP12/KEEL CLONE/ARO/AT33PTG with my semi DIY Evo/Buffalo II DAC, differences are far more related to the source recording quality than the format. Crappy LP's and CD's both exist as do sublime LP's and CD's. I prefer now the lack of surface noise and artefacts of the digital setup, but miss the hands on nature of LP replay. LP's inherently make you listen to music, where as with digital I still have the tendency to skip tracks I like less, which is in my view a negative. Of course I should add that the Evo/Buffalo combo trounces my CDX/XPS which has been mothballed!

    Regards
     
  20. Mike Reed

    Mike Reed pfm Member




    Groovy !:)
     

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