Angling for 90° - tangential pivot tonearms

Here's another idea, horizontally it has three pivot points which is a lot and may be difficult to make it work. The idea is to keep the split plane concept like the Dynavector but imagine the arm is extendable just like the one of two lines in the Thales triangle. But the guiding requires moving arm base with a magnet tracking, not touching, a steel rail below to keep the cartridge in tangent.

The red guiding arm is similar to what I proposed earlier with the tuning fork idea. Sorry again for the crude drawing.

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I am working on another idea that can will reduce the pivots.

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Hi again!
And thanks for pointing out the thread on the italian forum above. I just like to point out that I wasn't aware of it and had no intention to copy anyone without permission. In fact I got permission from Micha Huber to show that arm. And I had conceived it quite some time ago(together with various other solutions for pivoted linear tracking arms), mainly to combine the positive traits of the RS Labs arm with the zero tracing error offered by the Thales arm. I'll never be a commercial product, only built to find out if the added complexity outweighs the theoretical benefits. Which brings me to the "sound" of this arm.
Extremely tight and well controlled bass, mainly due to an effect that hasn't been discussed here. The arm-cartridge resonance frequency in the horizontal plane is nearly undectable if the thread tension(restoring force), combined with the inertia of the pivoting headshell+cartridge leads to an fres exactly at or near the fres with a fixed headshell. It acts as an anti-resonator.
Since the arm is so short(185mm eff. l.), energy storage/armwand resonances are very low. Image placement and specifity is exemplary. Build one and you'll hear how well it works.
Hope those italian DIYers get to read this as I don't speak or write italian. Don't want them to think I presented myself as the inventor of the Thales principle. Quite the opposite. Micha Huber deserves a lot of praise for his out of the box thinking.

All the best,

Frank
 
berlinta:"Which brings me to the "sound" of this arm. Extremely tight and well controlled bass, mainly due to an effect that hasn't been discussed here. The arm-cartridge resonance frequency in the horizontal plane is nearly undectable if the thread tension(restoring force), combined with the inertia of the pivoting headshell+cartridge leads to an fres exactly at or near the fres with a fixed headshell. It acts as an anti-resonator. Since the arm is so short(185mm eff. l.), energy storage/armwand resonances are very low. Image placement and specifity is exemplary. Build one and you'll hear how well it works."

Thanks for sharing your experience, Frank! I forgot to ask how well does it handle warped records since the armtube is so short and there's constant lateral force to the right which I imagine to be stronger than usual for it to guide within the Thales circle. I am looking into my pile of spare arms and parts for a good candidate for this experiment. I imagine an arm with no built in antiskating mechanism would work, like the Audio Technica ATP-12T, which unfortunately I sold last year. I have a Kenwood KD-770D that has a straight armtube with no offset angle that just might work...

I also wonder if unipivot is a good or bad idea for this type of design. Your arm is essentially a unipivot design so I guess it will work. The pivot point of the string will act as stabilizing the unipivot provided the height is matched to the main arm's pivot point.

Speaking of unipivot, I believe the new Thales Simplicity model lends itself to unipivot design since two armtubes in parallel can sit on two unipivot bearings without inherent azimuth rocking and certainly can simplify the design further.

Yes, credit must be given to Michel Huber for thinking outside of the box. I salute him! I believe the Italian forum poster is aware of the designer of the Thales arm and I appreciate him in investigating further into the genre. He's also aware of the contribution of the host, Yosh, of the Japanese website on this topic. I look forward to more ideas on such designs before we have to resort to air pumps and motors!

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Mark Kelly: "Arm design incorporating Burne Jones' Thales circle concept and Dynavector's split planes concept. This design fails for the usual reason: the complexity of the bearings creates excess friction or excess play (or both). Currently working on a new version incorporating a new concept which seems to avoid this problem."

I believe this patent by R.W. Birch can help reducing the number of pivots on the horizontal plane in this "split planes" concept, particularly figure 2.

http://www.freepatentsonline.com/3476394.pdf -- by R.W. Birch 1969

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Thanks for sharing your experience, Frank! I forgot to ask how well does it handle warped records since the armtube is so short and there's constant lateral force to the right which I imagine to be stronger than usual for it to guide within the Thales circle. I am looking into my pile of spare arms and parts for a good candidate for this experiment. I imagine an arm with no built in antiskating mechanism would work, like the Audio Technica ATP-12T, which unfortunately I sold last year. I have a Kenwood KD-770D that has a straight armtube with no offset angle that just might work...

I also wonder if unipivot is a good or bad idea for this type of design. Your arm is essentially a unipivot design so I guess it will work. The pivot point of the string will act as stabilizing the unipivot provided the height is matched to the main arm's pivot point.
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Hi again,
Warps appeared to be no problem. After all the arm is still many times longer than, say, a Souther, Revox or (part)Dynavector arm and the actual vertical pivot point is quite close to record level(unlike above mentioned arms)
Unipivots are (almost) as suitable as gimballed arms for the Thales thread assembly. Mainly due to the fact that the thread exerts very little force! The headshell bearing(s) need(s) to be of the highest quality. An additional skating compensation mechanism is beneficial since one can dial in a combination of (positive OR negative!)"conventional" antiskating force and restoring/antiskating force resulting from the hanging weight. Ideally if the hanging weight was chosen to compensate the skating force, the restoring force(the "tangential pull") should suffice too.
BUT!!! (ha, there's no free lunch..:) all bets are off once the headshell bearing is no longer perpendicular to the record. That's when you need the usually odd(read: clumsy) looking threaded rod/counterweight nose "extensions" to create a neutral balance pivoting headshell. Azimuth HAS to be adjusted by shimming one side of the cart or via a central, raised ridge on the bottom of the headshell(cart screws are just to adjust the tilt).
Changing VTA by raising or lowering the arm bearing is likewise problematic.
For a commercial product, the above spells DESASTER. Thank goodness we're surrounded by likeminded nuts :)
Wiring is the next problem. After looking at the pictures of the short arm, you can imagine that one doesn't want any "spring" connecting the headshell with the armwand.
Yup, there are easier ways to play a record, they're just not as much fun...

Cheers,

Frank
 
string theory

Another idea with string inspired by these string arms.

Let's have a pivot with wingspan above the headshell and two strings going along the armtube and tie to another pivot wingspan right above the horizontal pivot of the arm. Both pivoting wingspans are mounted on the same armtube so VTA is locked to each other and the two strings are tensioned at all times. And part of the wingspan sticks out acting as the guiding arm to force the cartridge close to the Thales circle. This guiding arm has to be slightly lower to match the height of the vertical bearing pivot point so movement can be precise. This can be implemented on arms like a Rega. The advantage of this is to shift most of the mechanism to the bearing area and also low mass. I haven't figured out the geometry yet but that's the gist of it.

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Two Strings or Two Arms

zeonrider: "Lovely! :cannotbe: . . . :worship: "

Sarcasm is not helpful in the experimental spirit. Oh, well...

ralphfcooke: "Instead of having the rear attachment points on the bearing assembly, would it not be possible to use a 'pair of cams' for the rear string to run around, thereby changing the angle by any amount desired?"

Thank you for the suggestion. You are right, a cam system should work. I was mainly concern about the vertical geometry because the main arm pivots up and down if any additional horizontal pivots not located at the height of the bearing will affect the vertical movement. My original idea was not well thought out, hence the mocking by Mr. Zeonrider. Hey, no laugh no gain!

After looking at the string system again, I realize there's no need to reinvent the wheel as the mysterious Japanese arm has apparently done all the homework by placing two static pivots around the main arm pivot point matching the same height. Brilliant!

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I guess in spirit the two-wand arm designed by Robert Van Eps is similar, just imagine the two strings are replaced with two wands. It would likely cost more to make. I think this arm would benefit from using a unipivot bearing for each wand and would simplify things. I suppose the Thales Simplicity tonearm fits into this two-wand arm genre.

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suitable arms for mod

I am always on the look out for reasonable priced tonearm for this type of experiment. Other than fair price, a good candidate should preferably have a straight arm wand (a curved arm works too, of course, but I prefer straight) and a detachable headshell so one can replace it without ruining the stock form, that is, the mod can be reversible.

I already mentioned Clearaudio's Satisfy arm but that's still pricey for me. After looking around, I believe a used Graham Robin (effective length 235mm) can work well since it has a straight arm wand for ease of headshell rotation and a detachable headshell (big advantage! almost identical headhsell on the Kenwood KD-770D) so one can swap in an experimental pivot headshell a la RS Labs or like the above string attached headshell.

The Robin is discontinued and has to be found in the used market. The Robin is a Jelco OEM arm so a Jelco SA-250st (effective length 228mm) , which is still available, (same as early Audioquest arm) should work but the headshell is fixed so one might have to drill a hole for adding a bearing for cartridge rotation. For it to be reversible, one might have to add a mounting plate for the bearing using the existing mounting slots, which will work the same on just about all fixed headshell arms out there.

The one advantage of the shorter Jelco is its 228mm effective length which can be slightly shortened to 222mm so the arm can fit on the same ubiquitous Rega mounting hole because that's the pivot to spindle mounting distance of Rega, which many tonearm set ups conformed to. Therefore the mod won't require new armboard or any mounting change. Of course, the experimental pivot-able detachable headshell for the Robin can be shortened as well to conform to the 222mm pivot to spindle distance.

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Hi,
You're mixing up eff. length with pivot to spindle distance!
The mounting hole for an arm of 228mm eff. length should be 209,8mm from the spindle, therefore your Jelco arm can't be used as as substitute for a Rega arm.
If, on the other hand, the p-s distance of the Jelco would be 228mm(again too far from the Raga's 222mm) its eff. length would come to 244,9mm. But to my knowledge(confirmed by the drawing), the 228mm figure refers to its eff. length.
Why Jelco decided to name that arm "SA-250" is a mystery to me...

Cheerio,

Frank
 
berlinta: "You're mixing up eff. length with pivot to spindle distance! The mounting hole for an arm of 228mm eff. length should be 209,8mm from the spindle, therefore your Jelco arm can't be used as as substitute for a Rega arm."

Frank, don't forget in an experimental arm like the Thales, there is no OVERHANG so whatever original arm's effective length will be the p/s distance. With an arm like the Jelco SA-250 that has original 228mm effective length, we can drill a hole at 222mm for the extra bearing for the pivoting headshell, therefore it will fit on the Rega original mounting hole, same p/s distance.

If one is to recycle an existing tonearm instead of starting from scratch, bear in mind the original spec of "effective length" has to be slightly modified or shortened in order to work because there is no overhang now. That's why I recommend playing with an arm that has a detachable headshell so one can use a beater headshell and experiment with mounting. In Frank's string experiment, obviously the string's tying point opposite from the headshell will be exactly doubled the length from the pivot point, i.e., 444mm for Rega.

Another thing to remember many typical 9" arms like the Rega has the vertical bearings angled at approximately 23 degrees to match the cartridge offset angle on a FIXED headshell to avoid VTA affecting azimuth, especially with warped records, but with a ROTATING headshell you will lose that benefit. Although I still prefer to have some bearing angle offset than none. The Thales has none. This is probably all minute and negligible but I just want to point that out because it is there.

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Regarding Jelco, they have made so many tonearms for other people that they never standardize an effective length for their 9" arms. Some 228mm, some 229mm, some 239 for the Sumiko MMT for example, 237mm for the Graham Robin, and who knows what else. Rather confusing as visually they all look similar, so check the original specs!


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Hi again,
Yup, I realize the overhang will be zero for a Thales type arm. But if you want to use the SA-250, you'd have to shorten the Jelco quite a bit, so much as to necessitate shortening the armtube by ~ 10mm. 40mm is roughly the minimum length required for a "headshell" with a pivoting mounting plate since many cartridges extend this far back(some even farther) and you don't want the cartridge pins to interfere with the exiting tonearm wiring nor should the thread start touching the headshell/armwand as the arm wanders towards the center of the record.
All of this shouldn't be a problem if you place the pivoting mounting plate so far below the centerline of the wand that the cartridge can rotate underneath the wand. But that would look kinda clumsy...
Good luck with your project!

Gone for a long weekend of audio....

Frank
 
berlinta: "40mm is roughly the minimum length required for a "headshell" with a pivoting mounting plate since many cartridges extend this far back(some even farther) and you don't want the cartridge pins to interfere with the exiting tonearm wiring nor should the thread start touching the headshell/armwand as the arm wanders towards the center of the record."

Thanks for the tips! I have thought of this "clumsy" issue and I think a straight arm will work better in this case so the rear end of the cartridge is angled outside and hopefully won't be touching any part of the arm before it wanders towards the record label.

You are right about audiophiles being nuts and that there are easier ways to play a record.... but where's the fun in that?! :)

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Bajulaz tangential tonearm

More fun vintage stuff from "Klangschloss Greifensee or the Sound Castle on Zürich's lake," 2010. One item is a vintage tangential arm. This strange tonearm is briefly explained in this site:

"It was designed by Ing. Bajulaz to overcome the geometry problems of the conventional tonearms, but allegedly it wasn't so good for the new stereo cartridges and therefore never went in production."


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Thales AV111 arm on Thorens TD-121 at the same event.
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Simplicity or not

A close up picture of the bearing of Thales Simplicity tonearm. I honestly think a pair of twin unipivot bearings will do the trick and will be much simpler. Because there will be no typical unipivot azimuth rocking due to the two arms tying together at the headshell. Of course, they have to show off their impressive precision watchmaking bearings.

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more Thales goodies

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http://www.audioexotics.hk - Pictures from a Hong Kong forum with listening impressions like below

POSTED by "Mr. Zanden": 18-12-2008 on AudioExotics

First home listening impression of "The One and Only Tangential Pivoted Tonearm"

Many months have passed since I last auditioned this uniquely patented design masterpiece and although my immediate impression of this product prompted me to order one almost 7 months ago because of its superior sound (I must admit it was very difficult for me to focus on the sound of the arm under a not-so-ideal listening environment and system matching), I didn't think too much of it afterwards as I was happy with my turntable with its matching air-bearing tonearm. Yes, I did temporarily swap out my Dynavector XV1-s with several other ones, the EMT was one of them BUT it was not a match made in heaven to say the least, after 30 hours of breaking in, I had to call it quits as the sound was uninvolving and light in balance - the latter characteristic was also easily discernable at PT's place and the rest (at PT's place) was history as PT subsequently found many compatible cartridges to macth different tastes and wallets.

I was very happy with my air-bearing arm as its tracking was its forte and its linear reproduction of sound was impressive, so all was well until my Thales finally arrived last Sunday, this is the x'mas gift my dearest other-half gave to me. For some reason I could not explain, I did not watch the assembly and mounting of this special arm (big mistake) and I only assisted Master Wei to adjust the huge & heavy (but moveable) arm tower to my turntable. A quick confession here, I only started doing regular very fine adjustment on speaker placement some 5 years ago and fine tuning my turntable system 3 years ago (subconciously I was too afraid to in case I screw up the arm and cartridge adjustment - but don't rely on others doing it for you either as turntable system is a mechanical devise, like a car and needs regular tuning to maintain its peak performance). After a bit of fine tuning, it was ready to hear the new arm with the new EMT gold cartridge.

Frankly speaking, the first few minutes of listening was a disppointment as the sound was not so dissimilar in tonality and information retrieval to my previous setup which I had just heard, I comforted myself by saying to myself perhaps it really needs to break-in both tonearm and cartridge for 30-40 hours b4 one can do any serious listening. I was wrong as after subsequent checkings, I discovered the wire connected to the tweeter on the right speaker was accidentally lossened during the installation, in addition, after adding a single thin wire for grounding purpose to reduce initial hum problem inadvertently shifted the arm tower, causing the tip of the needle to rest 2 mm beyond the tracking arch of the arm protractor.

Finally, after everything was set back to normal places (with NUMEROUS VTA, VTF adjustments and fiddling with tension of the 2 screws on the headshell), I began doing some serious listening. Whow, the sound was purer, more organic, better resolution , more 3-dimensional soundstage plus better bass resolution than my previous setup. You could almost hear everything which was recorded on the record, not that I could hear something (information) new which was not noticeable previously, everything came out naturally and you could hear the recorded information clearly without making any effort to listen to anything closely, in other words, you can follow every part of the music/playing with ease, just like when you are sitting in the fronts rows of a concert hall - is the sound of a tone arm with zero tracking error ?

I bought my first high end turntable in 1975, an Era (French) with the popular SME followed by Linn, Grace(then ITTOK and Syrinx) & Supex in 1976/77, my dream arm at that time was the world's most expensive swiss made Breuer (Micha of Thales has some relationship with this designer, so I was told). Since then, I had gone through many TTs, tonearms (including some older air-bearing and tangential designs). The point I'm trying to make here is I'm no spring chicken in the art of turntable playing (yes, when I visited many so-called vinyl lovers' homes, the sound of their turntable system was not perfectly tuned, some had the platter playing marginally faster than 33 1/3, some had slight mistracking, some had minor imbalance on the left & right channel and less-than-ideal VTA & VTF setting). Honestly, I find some hi-fi folks out there play turntable for the sake of showing to themselves or others that they are audiophiles but the sound of many of the so-called audiophile homes are rather mediocre (if you do not feel the same as me, then you may probably be one of them too).

My conclusion ( you can take it with a pinch of salt like I always do when I read other hi-fi reviewers' reviews) is the Thales is the best arm I have the pleasure of owning, it could possibly be the world's best arm but I can not and will never be sure of this but as long as I think it is, I can concentrate on maximizing the performance of my current turntable system. The Thales has made me aware of the design defiicency of the other arms I had used in the past, these include single pivot, tangential, tangential air-bearing and many others. A word of advice to those air-bearing tonearm users out there, air is the most tricky part after you have got everything done right (that means A LOT) because air CHANGES with temperature and humidity and last but not the least, pressure. Everytime when I used my previous air-bearing tonearm, I had to adjust the pressure, too much of it, the sound is less refine and may sound wee bit harsh on certain records, too little of it will impair the tracking esp. towards the end of the record - if you can't hear these subtle changes, good for you as you won't need to buy other designs. A turntable system is like a mini hi-fi system, if you don't get eveything right i.e. speaker placement and room acoustics, you can only hear 50% or less of what your gear is capable of giving.

Happy tweaking all you vinyl players out there but Thales rules okay !

Mr Z

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