Hi Direct driver, I tried to write an index of your great thread, indicating the initial pages of the main topics (from my viewpoint, of course).
As references I had to use mainly the various PLT typologies, because the theoretical part - which instead has a bigger importance - shows a karst like behavior, appearing and disappearing while discussing individual solutions or problems identified, so it's difficult to locate. Presently this index does not do justice to the quality of the scientific and technological contributions of the experts we all know and thank.
Hope other followers will correct / add their favorite topics; meanwhile perhaps we should point out the thread's "zones" where the various theories are discussed in depth. Not a simple task for my level of knowledge.
hope this helps - carlo
As references I had to use mainly the various PLT typologies, because the theoretical part - which instead has a bigger importance - shows a karst like behavior, appearing and disappearing while discussing individual solutions or problems identified, so it's difficult to locate. Presently this index does not do justice to the quality of the scientific and technological contributions of the experts we all know and thank.
Hope other followers will correct / add their favorite topics; meanwhile perhaps we should point out the thread's "zones" where the various theories are discussed in depth. Not a simple task for my level of knowledge.
hope this helps - carlo
Attachments
Hi Carlo,
I've been missing lately from this thread. I love your Rabbit tonearm idea (but I hate the rubber belt, due to possible slippage) and I went further and modeled in Linkage2 the gears version. On "paper" it works fine. It requires careful choosing of the gears (a sequence of 50T-58T-34T at 0.5 modulus gives the perfect 50mm distance between pivots). What I have not yet understood is if this tonearm has ant skating or not, since I've never seen you using some antiskating device. Does it go towards the label on a grooveless record or not?
I've been missing lately from this thread. I love your Rabbit tonearm idea (but I hate the rubber belt, due to possible slippage) and I went further and modeled in Linkage2 the gears version. On "paper" it works fine. It requires careful choosing of the gears (a sequence of 50T-58T-34T at 0.5 modulus gives the perfect 50mm distance between pivots). What I have not yet understood is if this tonearm has ant skating or not, since I've never seen you using some antiskating device. Does it go towards the label on a grooveless record or not?
Attachments
Interesting idea, and it's simulation looks really ok, Consty - congratulations.
2wice has done a remarkable work both on geometry (the Rabbit owes him a lot for this) and to avoid using the belt, first with three wheels, and then with cams; surely he could give you much more reliable information than me.
Belt - it never slips, and for a very good reason: Doug nailed it, and I glued it to pulleys. But also left free it slips only by setting up the TA, never during tracking. So it's just to avoid the tiresome realignment after some silly maneuver that we did it so.
Gears - it doesn't excite me, not only for a higher friction (belt <<5%), but more for the unavoidable micro-play = chattering.
Skating - geometrically it's there for sure (string test failed) but it's behavior is complicated - look at # 1733 -vector breakdown - which tried to understand what happens. However maybe on PLTs the stylus drag is used almost entirely to guide/rotate the arm, and therefore just a negligible quantity remains to produce skating*.
Keep us informed - carlo
*The blank disc test (as long as it is a test ...) for me it is even more useless with PLTs that have two possible movements (advancement + rotation)
2wice has done a remarkable work both on geometry (the Rabbit owes him a lot for this) and to avoid using the belt, first with three wheels, and then with cams; surely he could give you much more reliable information than me.
Belt - it never slips, and for a very good reason: Doug nailed it, and I glued it to pulleys. But also left free it slips only by setting up the TA, never during tracking. So it's just to avoid the tiresome realignment after some silly maneuver that we did it so.
Gears - it doesn't excite me, not only for a higher friction (belt <<5%), but more for the unavoidable micro-play = chattering.
Skating - geometrically it's there for sure (string test failed) but it's behavior is complicated - look at # 1733 -vector breakdown - which tried to understand what happens. However maybe on PLTs the stylus drag is used almost entirely to guide/rotate the arm, and therefore just a negligible quantity remains to produce skating*.
Keep us informed - carlo
*The blank disc test (as long as it is a test ...) for me it is even more useless with PLTs that have two possible movements (advancement + rotation)
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I'm doing my best
You are absolutely right. Gears is not the way to go. Belt is much better. I am already working on it. But before starting to invest time and effort I wanted to know exactly what's to be gained by using this Rabbit geometry. Especially since some posts on different forums even try to discourage us, the "tangentials". They say something like "Since 99.99% of all the turntables sold and even those high end ones are using the classical pivoted tonearm, why would you struggle for a tangential one?". That made me improve my initial Linkage simulation and measure everything. The file is attached. That improved version has also allowed me to make a direct comparison between the famous Lofgren A and B alignments and the Rabbit. The result is also attached and IMHO, it is remarkable!
Attachments
"Since 99.99% of all the turntables sold and even those high end ones are using the classical pivoted tonearm, why would you struggle for a tangential one?".
"..not because they are easy, but because they are hard..."
as one great President said, talking of the moon landing. But, given the due proportions, the motivation is the same for us small diyers too: linear trackers and PLTs are a far more interesting challenge, both from a theoretical and a constructive point of view.
I have once confessed that I do not consider either the Rabbit, or the Lilcasey the arms that sound better among many I have built (the more convicing is the 3Points, a Baerwald with a very particular articulation) but they certainly were much more interesting and instructive to build, both from the design and construction point of view.
Geometry - It is not a tracking error problem (it's evident that is extremely less) but the price to pay in terms of variable forces and frictions (side force versus skating an so on); but the discussion is so complex that we are talking about it from some thousands of posts.
Now back to the Rabbit: the gears are not wrong per se, but the problem is that on the eccentricities the shaft goes back, and this starts the unavoidable play of the gears.
Here attached the simulations of the original Rabbit and 3D Rabbit. You have to avoid extending completely the arm, for the reasons highlighted in my #1733 hypothesis.
"..not because they are easy, but because they are hard..."
as one great President said, talking of the moon landing. But, given the due proportions, the motivation is the same for us small diyers too: linear trackers and PLTs are a far more interesting challenge, both from a theoretical and a constructive point of view.
I have once confessed that I do not consider either the Rabbit, or the Lilcasey the arms that sound better among many I have built (the more convicing is the 3Points, a Baerwald with a very particular articulation) but they certainly were much more interesting and instructive to build, both from the design and construction point of view.
Geometry - It is not a tracking error problem (it's evident that is extremely less) but the price to pay in terms of variable forces and frictions (side force versus skating an so on); but the discussion is so complex that we are talking about it from some thousands of posts.
Now back to the Rabbit: the gears are not wrong per se, but the problem is that on the eccentricities the shaft goes back, and this starts the unavoidable play of the gears.
Here attached the simulations of the original Rabbit and 3D Rabbit. You have to avoid extending completely the arm, for the reasons highlighted in my #1733 hypothesis.
Hi Consty,
Don't let the Nay sayers on this website discourage you. If we listened to the 99.99%, we would still be living in caves with burlap sacks for doors.
Sincerely,
Ralf
Thanks for the two attachments. But the 3D one makes me wonder: Is this an older version? Why 24:16 gear ratio? Indeed, 1.5:1 is an easier ratio to attain than using a ratio involving a prime number.
When I'll have some time I'll make the same angular error graphing as I did for the 25:17 one.
Of course complete arm extension is not feasible, but luckily it's also not needed because it takes place when the needle is over the record spindle
Well... Probably the digital enthusiasts are saying exactly the same thing about some guys listening to a needle scratching spiral ditches on a plastic surface
No, Consty - it's the geometry of the 3D Rabbit, the printable version of the Rabbit. # 1950.
The Rabbit's geometry was found with row & compass, and then fine-tuned thanks to the precious help of 2wice. Subsequently, thanks to Linkage2, I verified various geometries #1016-17-18, and made several attempts to improve the Rabbit's original one.
The ratio is what you've found, and the distance goes from 50 to 54 mm, if I remember correctly. It is something better than than the original, but if you can't turn yourself the pulleys, the ratio 2:3 goes very well the same.
ciao Carlo
Digital natives have lots of reason, but can you compare the turntable's magic with an Iphone? they themselves are now running to buy vinyls and turntables.
And since I am a fundamentalist diyer, it seems difficult to be able to fabricate a microchip at home ...at least with these old eyes
The Rabbit's geometry was found with row & compass, and then fine-tuned thanks to the precious help of 2wice. Subsequently, thanks to Linkage2, I verified various geometries #1016-17-18, and made several attempts to improve the Rabbit's original one.
The ratio is what you've found, and the distance goes from 50 to 54 mm, if I remember correctly. It is something better than than the original, but if you can't turn yourself the pulleys, the ratio 2:3 goes very well the same.
ciao Carlo
Digital natives have lots of reason, but can you compare the turntable's magic with an Iphone? they themselves are now running to buy vinyls and turntables.
And since I am a fundamentalist diyer, it seems difficult to be able to fabricate a microchip at home ...at least with these old eyes
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Dear directdriver,
Rube Goldberg toy or not, the concept is not at all new. See this 6 years old post: Schuch Tronic's "The Perfect Pick-up Arm | Analog Planet about Daniel Schuch's almost identical design.
But this is not the point of my comment. As soon as I saw the pictures you posted, I have immediately modeled this tonearm in Linkage (attached). Even though I was initially skeptical about their marketing claim "NON Error Tracking Tonearm Exact Trace", the results I obtained are truly exceptional! With the proper pulley ratio: 0.00 degree angular error from 0 to 183mm record radius!!! With this design you can even play studio transcription records without any tracking error!
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You obviously haven't gone through the whole thread. We covered the Schuch arm already, even his other versions. Schuch is not the only one uses string (our member inventor Andy might have something to say about that!) but that requires you to browse through nine and half years worth of posts!
Just about everything in the market of the tangential pivot tonearm genre has been covered in this thread. The point of the 47Labs post is that the arm is new and was introduced in early 2019 so I have to update it here. Also, 47Labs is known for Rube Goldberg contraptions not just tonearms (they also distribute the RS Labs RS-1A arm with the swiveling headshell) but other components as well such as their turntable with counter rotating platters, etc.... It's part of their marketing strategy.
Well... Probably the digital enthusiasts are saying exactly the same thing about some guys listening to a needle scratching spiral ditches on a plastic surface
Hi Consty,
Who's side are you on, anyway?
Sincerely,
Ralf
Hi Consty - I can't make the two last simulations work - block signal at the starting point - where i'm wrong?
However, TAs like this new 4743 in their various reincarnations (Polygon, Thales Guy etc. included), in spite of their accurate geometry do not convince me for these reasons
- mechanical complexity
- very substantial vertical effective mass (weight loaded in the worst possible place)
- rotating head shell - the bearing so near to the stylus is the most critic point, imho.
This too was extensively debated along this thread.
carlo
Who's side are you on, anyway? (Ralf)
for those who can't decide .... why not to try this
YouTube
seems a nice compromise isn't it? what I've most appreciated is the "tube" touch, ... and the similarity with my avatar.
However, TAs like this new 4743 in their various reincarnations (Polygon, Thales Guy etc. included), in spite of their accurate geometry do not convince me for these reasons
- mechanical complexity
- very substantial vertical effective mass (weight loaded in the worst possible place)
- rotating head shell - the bearing so near to the stylus is the most critic point, imho.
This too was extensively debated along this thread.
carlo
Who's side are you on, anyway? (Ralf)
for those who can't decide .... why not to try this
YouTube
seems a nice compromise isn't it?
what I've most appreciated is the "tube" touch, ... and the similarity with my avatar.
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Hi Ralf,Hi Consty,
Who's side are you on, anyway?
Sincerely,
Ralf
I thought it's obvious by now
I'm totally appalled by the way MP3 has distorted the way humans perceive MUSIC. I'm sure every youngster you see in the street with the earphones plugged to their mobile phones would be thrilled to listen for the first time to a decent audio chain. As much as I was when I saw for the first time a color TV set after 25 years of B/W
. It's that kind of unforgettable once-in-a-lifetime experience.Indeed, Ipod made music portable, fitting a whole records shelf in your pocket the same way Kindle fitted a whole library in your pocket, but at what price...
Quantity vs Quality
BUT, during my almost 60 years of life, I've learned that:
1) One of the secrets of happiness is: Never take yourself too seriously
2) A little bit of self irony will never hurt a smart person. It helps a lot in keeping us grounded and rooted in the fast changing reality surrounding us.
Yours,
Consty
Hi Carlo,
Sorry to hear that. You're probably not wrong at all. What Linkage version are you using? I have just installed the latest version I found on their website (3.10.11 64 bit) and it works fine on my Windows 10. Are you using Windows or Mac? I'll post soon for you a video of my 47Labs TA Linkage simulation.
Regarding the disadvantages of this design, indeed, I'm not very happy with ball bearings just above the cartridge. That's one of the main reasons I abandoned Micha Huber's Thales design (even though it produces perfect alignment) in favor of the Rabbit. The same applies for this one. On top of that, who knows what resonances may produce a violin string attached to a tonearm
Regarding the YouTube video you linked, it's really sweet
What I like the most is the USB cartridge
Yours,
Consty
Say, I do believe I see a string-and-weight antiskating device on this arm. With the way the AS weight string is attached to the bearing yoke, it will correctly apply compensation force outward away from the spindle at the outer grooves, zero compensation in the middle, and compensation force inward toward the spindle at the inner grooves.
Ray K
https://www.diyaudio.com/forums/attachment.php?attachmentid=794307&stc=1&d=1573580255
