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Sideways Uni-Pivot Arm, SUPATRAC Blackbird, formerly "Ekos Killer (Price?)"

Discussion in 'audio' started by sonddek, Sep 20, 2020.

  1. sonddek

    sonddek Trade: SUPATRAC

    It's a very small issue, possibly inaudible, and it is fixed by a very small adjustment in hoist angle.
     
    Rockhopper likes this.
  2. yuckyamson

    yuckyamson pfm Member

    Again, sorry if this is creating "noise" in the communication (pun intended), but do I have it right that you've now made the hoist sit vertical (i.e. no underhang), and thus the only effect when twisting left/right away from "record middle" (call it "track 3") will be one of skate/antiskate, which you're adjusting for in your antiskate mechanism. Correct?

    I kind of liked the underhang to apply forward pressure from the thrust plate onto the pivot point. If you're now using a magnet, is there a chance that as the pivot swings l/r ever so slightly that the magnet will not have continuous effect on the pivot? That it could be pulling it one-way or the other, rather than just at the thrust plate?
     
  3. sonddek

    sonddek Trade: SUPATRAC

    Yes, correct.

    The magnet will be optional, just as it was in my prototypes. Some people may decide that the degree of lean variation is barely or not audible and prefer to use the arm without a magnet for simplicity's sake.

    The requirement for very light pressure at the pivot point is or can be supplied in three ways: stylus drag (not optional), gravity/underhang (optional) and magnetism (optional). My view is that stylus drag is not enough on its own to guarantee good performance unless you tilt your deck, in which case you're using gravity but not underhang. If you use too much underhang the rotational plane of the arm and record do not match perfectly and there will be a tiny variation in lean across the record.

    I intend to send both a stainless steel (tungsten-tipped) pivot bolt and a magnetised mild steel (tungsten-tipped) pivot bolt with each arm. A small magnet can also be placed on the end of the pivot bolt to increase the pull at the pivot point. The magnetic pull is small, but enough, so although you are right about variation in the pull of the magnet as the arm yaws, the angle of use is 18º or less, and I do not expect this to be a source of significant error in skate forces, especially when you consider that correct skate force is also signal-dependent. Roughly right net anti-skate, the best that one can do on any pivot arm, will remain roughly right net anti-skate.

    Either way, with a light touch of magnetism or underhang, the arm will continue to produce astounding performance. I hope that all makes sense.
     
    Last edited: Oct 25, 2021
  4. yuckyamson

    yuckyamson pfm Member

    It makes sense. Without having used it, I'd be more inclined to use underhang than add a magnetic field into the mix, but that's all just in my head and if there's one thing I've learned, it's that the imagined physics of audio don't always translate when you try something and listen to it, and learn from there. The bottom line is that Adam said that this arm, in no uncertain terms, was better than his ekos, aro, and javelin, and he wasn't making any bones about it. So that to me is high praise. Perhaps in future iterations you will have a more refined version, or another solution still implimenting the sideways unipivot. I rather love the concept.
     
    sonddek likes this.
  5. sq225917

    sq225917 Bit of this, bit of that

    It's a unique approach to the task at hand and one that does away with most of the issues that plague certain unipivot designs and chattering gimbal arms.
     
    sonddek likes this.
  6. sonddek

    sonddek Trade: SUPATRAC

    At LencoHeaven Billy says it is better than his Audiomods 6, Arndt thinks it helped him install what some said was the best system at the Berlin Audio Meet, and about ten people have made clones of varying sophistication, all of whom report unprecedented performance. More arms are going out as I produce, and I now expect there will be many more surprising reports. Meanwhile I don't get enough time each day to listen to those archaic black discs! ;-)
     
  7. sonddek

    sonddek Trade: SUPATRAC

    I don't know when 'production' can be said to have started, but I'm 'gearing up'...

    [​IMG]
     
    Dirkster, Plink, joe9407 and 3 others like this.
  8. sonddek

    sonddek Trade: SUPATRAC

    A brief update: for the time being, only the Death Star thrust boxes will be available for new orders. The Aero version may be available again in the future, but probably not for a few months. The reason is simply to do with ordering batches of parts, as I'm sure you will understand. If you're desperate for Aero, then I can make one for you, but I will have to charge an additional fee because of the time it takes me to make parts myself instead of having them made elsewhere. All thrust boxes are now painted and have channels to make room for vertical hoists/magnetic bearing contact.
     

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