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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

    Amen.
     
  2. Joe Hutch

    Joe Hutch Mate of the bloke

    Never had any end of side distortion, except on Raw Power which is distorted all the way through. Can't even be arsed with ripping my CDs so there's no way I'll be digitising my LPs.
     
  3. Basil

    Basil Harbethian

    When was the last time you checked your tweeters were working?







    ;)
     
  4. Joe Hutch

    Joe Hutch Mate of the bloke

    Even if my tweeters are working perfectly, my ears are knackered.
     
  5. Basil

    Basil Harbethian

    Perhaps it's gods way of telling you to stop listening to Céline Dion?
     
  6. Nik

    Nik pfm Member

    No. The whole point of offset-and-overhang geometry is that it allows two such points, minimising tracking error over a much greater range for a given arm length. You can, if you wish, set an arm up for zero error at only one point but that would be somewhat perverse as you would increase tracking error everywhere else.
     
  7. sonddek

    sonddek pfm Member

    The "angle of a record's groove", whatever that means, is not the origin of the need for an anti-skating force. That's a misunderstanding.

    The anti-skating force compensates for the tension in the arm which pulls the stylus more heavily against the inner groove, due to the position of the arm pivot. This imbalance would still occur if you replaced the record with a straight track. Let me repeat that to be clear: imagine that instead of a record you created a long grooved vinyl 'tape' which was dragged under the stylus. Imagine also that just as with the record, the arm's pivot was displaced sideways (towards the side where the spindle would have been). The anti-skating force will still be required even though you are playing a dead straight, non-circular medium. That's because the arm can only pull towards its pivot, which means it pulls more heavily against the inner groove than the outer. Here's a diagram to make that clearer:
    [​IMG]
    So anti-skating force would still be needed if the record was in fact a straight line. (From the stylus's point of view, it is.)

    During playback of a record, the offset (perpendicular distance from groove tangent to arm pivot) doesn't vary very much, so, all else being equal, the anti-skate force shouldn't vary either. Let me be clear what I mean by offset. I am referring to the distance between the arm pivot and the tangential line extending from where the stylus meets the groove, as shown in the diagram.

    A sudden loud passage almost certainly increases the drag on the stylus, and anything which increases drag on the stylus will need a corresponding increase in anti-skating force. So correct anti-skating force varies from one second to the next in normal music. It varies with stereo imbalance since a stereo record has differing drag on each side of the groove, it varies with vinyl texture, it varies with temperature and so on. Consequently, anti-skating is a very crude average. You might set it correctly for a mono track 3, but it will be wrong elsewhere on the disc, sometimes by a large divergence. That's why some manufacturers say it doesn't matter. It's never right, and yet somehow the record produces spellbinding music.

    I know of no examples of pivot arms where anti-skating is accurately maintained.

    Note that he says groove velocity affects it, but then draws the wrong conclusion at the end, unless he thinks higher groove velocity produces less drag.

    I don't believe this. It might be so with entirely silent tracks, but as soon as you have musical content you have the likelihood that drag increases with groove velocity. As I've said, you can test this with a conical stylus by observing the movement of the stylus when it is placed on the flats at the beginning and end of a record. Better still, if you have a blank pressing it's very easy to see. When anti-skating is balanced at the track three position, track five will cause a centrifugal movement, and track one will produce a centripetal movement. Don't take my word for it - try it. This shows that an inadequate anti-skating force at track one is an excessive one at track five. Ergo correct anti-skating should reduce as the record is played. The reason is clear: drag is proportional to radius (plus some other function).
     
  8. sonddek

    sonddek pfm Member

    I'm glad you could be bothered to say that. I ran out of steam trying to explain anti-skate.

    Can anyone tell me what the typical maximum tracking angle error is with well known alignment schemes? In degrees or radians? Thanks.
     
  9. FFFF

    FFFF Active Member

    From the Avid site:

    Recently 12" arms have come back into fashion, claiming lower tracking distortion. However whilst in theory this is correct in the 'real world' this rarely happens and there are also the downsides to take into account.

    Average distortion on 9" arms is 0.85%, whilst 12" arms are 0.67%. Some trying to impress will say this is 20% lower distortion, however this is incorrect as in real terms its only 0.18% lower.

    Now add to this the downsides of higher moving mass, lower arm rigidity, higher counterweight inertia and worst of all higher distortion caused by misalignment.

    Yes...in the real world rarely are styli correctly fitted within the cartridge body and most fit their cartridge using a standard alignment gauge using the body as a guide. Therefore if your stylus is misaligned within the headshell the distortion will be greater using the 12" arm as the distance from pivot to stylus is greater.

    Record damage is greater due to counterweight inertia, warp tracking worse by higher moving mass and sonic degradation caused by unwanted structural resonance’s in longer arms, coupled to having oversized turntables causing more issues.

    And you still want to use a 12" arm ?
     
  10. Nik

    Nik pfm Member

    "Could be bothered"? I was just surprised no one else picked up on it. :)

    For a 9" arm we are talking about +2° at the outside, passing through -1° in the middle of the playing area, then around +1° at the inside. Exact figures depend on where you choose your zero points and the actual max and min radius of the playing area, which vary quite a lot.

    BTW are you missing something with your "blank disc" test? I think you assume bias compensation ("anti-skate") is constant but I think virtually all bias compensation devices produce a varying force as the arm moves across its arc, so is the test valid?
     
  11. Rasher

    Rasher Quadrophenia land

    I don't get this. I understand the OP, but this is getting beyond the brief.

    Accurate doesn't come into it and it can't because there are so many variables including the ears of the engineer that mixed the recording in the first place. If the goal for sonic nirvana lies with a distortion and colouration free sound, then you'd better set yourself up with some sort of lab and an oscilloscope or something, but music isn't going to have much to do with it. Music isn't a science and it shouldn't be this sterile.

    It's great to be inventive and apply a bit of boffinism to arm geometry, but it only comes down to what sounds satisfying to the listener, which goes a long way to understanding why LP12s are so popular. They are flawed, but people like the noise the flaws make.

    Personally I don't give a stuff about whether something is correct or not - I only care about if it sounds good to me, and I particularly like the fact that LPs can sound so great when a disc of plastic with a pin scraping over the surface really shouldn't at all. Digitised music can sound great too, but it's all a bit too sanitised in the science for me to get excited about.

    I like the journey of getting results by fiddling, and don't want a digital perfect fix to everything hi-fi, anymore than I want to fast forward to my death-bed with a silver disc of ready made memories clutched in my hand. The journey is the fun bit and the getting there is the disappointment that it's over.

    If digitisation is near perfect then you can keep it, because I'm not ready yet - and just because of that I'm going home to mess up my anti-skate setting so I have to start over.

    :)

    p.s What Nik said above - messing about with +2 degrees, 9", 12" arms, correction etc. That's fiddling with soul. That's where the fun lies.
     
  12. Rasher

    Rasher Quadrophenia land

    There is Scientific, and then there's Garden-Shed Scientific.
    If you are British, you'll understand.
     
  13. sq225917

    sq225917 Bit of this, bit of that

    Bloody hell couldn't Avid just write we can't fit a 12" arm so ner, ner, ner, ner.

    Not to split hairs, but the typical reduction in tracing error is up to 1/5, he can write it anyway he wants, saying it's only 0.18%, but that is the absolute reduction, in real terms it's a reduction of 1/5 of the total distortion and saying it any other way is misleading.

    A longer tonearm actually reduces the effects of misalignment due to the flatter arc it traces than a shorter arm.

    If he can't set an arm up using a point protractor how the hell does he design a turntable worth a lick?

    That's a great bit of scaremongering, no more, no less, because he cannot integrate a longer and heavier arm onto his designs without a complete overhaul of the suspension and underlying design.

    sad really.
     
  14. mmaatt

    mmaatt pfm Member

    Ok so disbelieve the experts as well as two highly respected tonearm designers: The Continuum Cobra arm also increases anti-skate from 8% at the start of a record to 12% of VTF at the end. Your explanations as they stand seem fine but incomplete that is all, and from several sources it has been found that groove velocity has no effect on skating force.

    mat
     
  15. sonddek

    sonddek pfm Member

    OK, interesting - I don't doubt that Caliburn got it right, but I would love to see the reasoning, because it makes no sense from the basic physics.

    Can someone suggest a factor that might increase the drag coefficient towards the end of the record?
     
  16. Mike Reed

    Mike Reed pfm Member

    Are you saying that Avid decks can't take 12" arm? I find this hard to believe in a series of turntables costing up to the teens of thousands.

    Mind you, I guess that all suspended decks (incl. my Orbe) need a bit of TLC to balance out the bounce factor. A plus for non-suspended decks, I s'pose !
     
  17. mmterror

    mmterror pfm Member

    Meanwhile all the CD folks have though life it too short, have quietly sneaked out and gone off down the pub for a pint..........
     
  18. afewbeers

    afewbeers more sense than money

    This surprises me also; I have been thinking about the possibility of moving to a 12" arm (SME) and have been considering an Avid. I find it hard to believe that an adapted arm mount could not be manufactured to achieve this. Obviously there will be a trade off with redistributed mass etc but I'm sure it could be achieved.
     
  19. sonddek

    sonddek pfm Member

    ...and a lengthy chat about, jitter, nyquist, and error-correction.
     
  20. John

    John Fore!

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