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Is this the best tonearm in the world?

Discussion in 'audio' started by G T Audio, Mar 9, 2023.

  1. Paul R

    Paul R pfm Member

    I don't take it as given that a belt drive slows noticeably when the pianist hits a chord. I think it needs to be shown. There's no intrinsic reason why it should.

    But the one thing that is obvious in engineering a turntable is that the ideal answer is direct drive. Every other drive method introduces problems that then have to be solved, or at least ameliorated, so if designing you simply wouldn't do it other than if forced to for budget reasons.
    nmtjb likes this.
  2. dave charlton

    dave charlton pfm Member

    Rega call their latest an EBLT, used in one's, two's and three's.
  3. yespsb

    yespsb pfm Member

    That's one of the daftest things I have read in a long time. How the hell can a load, whether its small or huge result in "infinite" stress ? The resulting stress on any given structure will always be proportional to the load, the construction material and it's design.
    And before we all forget, we are talking about tone arms, not sky scrapers or some part of part a NASA rocket. Would you care to tell the forum what you believe the load range is on a tone arm ?
  4. tpetsch

    tpetsch The Rhythm has Control..

    There's no doubt that belt driven & to some extent DD decks both exhibit stylus drag. The thing is how they maintain their speed or push thru during the drag event. In other words for argument sake, when the platter is aloud to spin freely -stylus not in the groove- the platter may be spinning/maintaining perfectly at 33.34 RPM, then once the stylus drops onto a spinning record the RPM's may drop to say 33.31, the better engineered decks/platter shape-mass/motors/powersupplies don't jump back and forth from the original 33.34 to 33.31 during the heavy transients for example, they just fall to 33.31 and maintain it continually for the most part. I personally use a wall strobe RPM checker -like in the video below- and simply adjust the platter RPM's with the stylus in the groove while the LP is playing. IMO, I'd be more concerned about what the auto speed correcting decks do to the playback performance.

    Watch from 2:40 to see a stylus drag demo in real time, notice how the drag starts instantly, then maintains before the music/transients even begin, for the most part. I've also witnessed this on my own deck:
  5. tpetsch

    tpetsch The Rhythm has Control..

    Yes, I understand they are all "belts" but the curious observer will note that the cross section of a flat belt vs O'ring type "belt" are very different. Pull on a flat cross section belt such as an LP12 belt and see how it stretches by pulling the wide section thinner from the flat section at different rates, then pull on a perfectly round cross section O'ring and see how it uniformly stretches equally around its circumference. ...It's the little things.
  6. Tony L

    Tony L Administrator

    There is absolutely no doubt that stylus drag exists as a force. There is also absolutely no doubt that it is a variable too; the degree is impacted by the groove modulation amount, plus other factors such as warps, tracking force etc. There is simply do disputing either point. It is friction/drag at a comparatively easy to understand level. If in any doubt compare the spin-down time of a) an unloaded platter, b) the stylus in the run-out groove, and c) tracking a densely modulated section of a loud 12” single. Three different figures.

    The question is how best to counter it, e.g. where the ideal balance of torque and rotational mass lies?

    Whilst it is great fun to take the piss out of rubber band-driven record players, and I obviously approve of doing so, enough of them are actually very good from a subjective pitch/timing perspective so can’t be doing that much wrong. I’m obviously a vintage idler fan, I’ve been running one for well over a decade now, but I’m still confused as to whether it is a simple high-torque thing I like as I always thought my old Xerxes had really good pitch and timing (very low torque, motor on a spring!), P9 too, yet I didn’t get on with an SL1200G I briefly tried (extraordinarily high torque, you could likely use it as a woodworking lathe!). As such there is more to this than I necessarily understand, though my ancient TD-124 has such a good combination of pitch, timing, life, slam etc that I’m no longer looking. It is all just curiosity at this point. Analogue replay is a fascinating thing!
  7. Mike Reed

    Mike Reed pfm Member

    I haven't noticed stylus drag on my Dais (VTF 2g) but maybe the heavy platter was Tom Fletcher's way of counteracting it
    sq225917 likes this.
  8. sq225917

    sq225917 Bit of this, bit of that

    The idea of torque in any record player is wide of the mark, once up to speed the motor provides almost zero torque to keep it spinning.

    If you have a high drag viscous bearing stuffed with thick oil then it's a different tale.
  9. tpetsch

    tpetsch The Rhythm has Control..

    You'll see it with a strobe checker like in the video where you can measure RPM's down to thousandths due to the wider possible testing diameters. If you have a strobe meter flashing & moving slightly on a wall 2-3 meters away your measuring extreamly fine increments in real time, you might not instantly see tiny movements from a foot away from the spindle, but flashing across the width of a room those tiny movements become more obvious. And BTW did you happen to notice how heavy the platter was in the video?
  10. Paul R

    Paul R pfm Member

    The existence of stylus drag isn't in dispute. Its dependency on groove velocity isn't in dispute.

    Its significant variability with groove modulation is however being assumed.
    And that there's something unique about a belt drive that makes it unable to control that supposed variability.
    Which was the assertion in the OMA video.
  11. tpetsch

    tpetsch The Rhythm has Control..

    I don't believe any deck can 100% completely control that supposed variability. The best engineering can do is try to deal with it as best they can all while making it affordable within bounds for the consumer. And like I mentioned the main stylus drag load is instantly when the stylus meets the vinyl and then continues at a new rate, no music needs to be present just a modulation free groove. I have yet to see/hear for myself -on my P10- to what extent the then added on top of that transients/modulations effect the RPM's, I have no doubt that they do but they're nowhere near to the extent of initial and then continuous drag of stylus in the bare groove alone, then it's up to the quality/engineering of the deck to maintain and push thru after taking that initial load/drag into account.
  12. Tony L

    Tony L Administrator

    As I say above you can measure spin-down time assuming the deck has a free-running platter, different figures for stylus not on record, playing blank groove, playing heavily modulated groove. It is exactly as logic would suggest. The more drag the quicker the platter stops. I remember timing it back when I had the 301 in a very solid slate plinth, though can’t recall the figures.

    I’m sure figures could be obtained for the same three states with pretty much any (non-servo controlled) playing deck too with a strobe disc in a similar way to the ad for the projection thing upthread. A locked direct drive deck such as a Technics just corrects on the fly. If it detects any slowing it increases motor torque (and with an incredible amount on tap!).

    PS I may not have used the term ‘servo’ in the correct context, I’m pretty sure it has other applications, though if you’ve ever played around with any SL1200 MkII or later they really fight back if you try to slow the platter! They definitely react dynamically to changes in drag.
  13. sonddek

    sonddek Trade: SUPATRAC

    There is AES research on stylus drag. There's a graph of drag against signal level. It sure ain't flat. Looks more like a group of exponents. It varies between cartridges, but signal strongly tends to be quite a big factor. There were a couple of cartridges which produced much lower drag, can't remember which - possibly very high or low compliance or downforce - but signal was still a factor. I imagine the graph was produced by some kind of strain gauge.
  14. tpetsch

    tpetsch The Rhythm has Control..

    With all do respect spin-down of a free spinning & undriven platter vs. driven motor/torque assist pushing thru after the initial stylus drag load has been factored in are very different animals, then add multiple belts -or O'rings" and other engineering tricks designers may use to help combat this issue.
  15. sonddek

    sonddek Trade: SUPATRAC

    I found it, thanks to Paul on Lencoheaven for bringing this to my attention:

    The cartridges with rather special performance in this regard were Deccas, but they have a reputation for being a bit wild when it comes to difficult grooves. They probably throw a lot of energy at the arm bearing due to unusual compliance.

    Recently Arndt at Lencoheaven has posted about the results he is getting with his Deccas on an arm which he made himself. It has a sideways uni-pivot bearing:

  16. Tony L

    Tony L Administrator

    I’m not arguing against any of that, just stating categorically that the phenomenon exists and is variable in nature. How that translates will obviously be very different in differing turntable, arm and cartridge scenarios. This is the point it gets interesting as there are so many seemingly conflicting ways to make a good record player. I cited the Xerxes as an example up thread as I honestly have no idea how that thing can play in tune given stylus drag, yet it does, and well! Even though I’m in the vintage idler camp I think there is more too this than simply throwing torque at it.
    tpetsch likes this.
  17. matt j

    matt j pfm Member

    Would stylus drag not also be vastly effected by VTF? In which case how can it possibly be accounted for with various mass platters, drive systems and tracking forces involved?

    Are we not into the realms of tuning a specific TT/arm/cart combo here and not what can be expected from general manufacturing?
  18. Tony L

    Tony L Administrator

    So, Walter’s Beethoven 3 is a bit of a drag (Discogs).
  19. Mike Reed

    Mike Reed pfm Member

    For me, having the strobe disc on whilst the platter was revolving and with the designated light shining down, it's easy to see any 'slowing up'. Simply altering the Wave Mechanic controller a tiny bit shows up clearly, yet lowering the stylus doesn't. That's not to say there's no drag, but what there may be is visually (and audibly) undetectable. Good enough !
    Last edited: Mar 18, 2023
    Darren likes this.
  20. Vinny

    Vinny pfm Member

    Weight of any platter? Dais platter?
    The frictional drag of the stylus is going to be in the order of 1g - somewhere close to 0.7 x tracking force.

    Do the sums, although the effect will diminish as the record plays.

    In fact, you don't have to, the difference is so unimaginably negligible - plus and minus the friction, unless someone is using a TT with a very thin balsa platter.

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