Hello Nanook,
Please don't get me wrong. I'm fully aware of the neccessity to implement an offset angle to keep tracing error related distorsions as low as possible. That related math is 50years and older. What remains is that any correction mechanism, aka "antiskate" will preload the cantilever in the horizontal plane, on some unipivots a much smaller vertical component exists as well. An excursion in one direction, say right, will require more force than one in the opposite direction. Similar to a speaker/driver with an asymmetrical suspension characteristic(essentially all cone drivers).
There simply is(almost) no way to compensate for the skating force at the stylus tip.
What you describe regarding turning my arm into an "active" device is covered in the patent application. It complicates matters, leads to the old "error before correction" problem or requires some very clever correction algorythm, but, most importantly, sounds no more transparent.
"The key is that whatever the orientation of the headshell/stylus tip at the initial state was, it should remain in that state. " Yes.
"This could be accomplished by allowing only vertical travel of the arm, while the base provides the rotation." No(or maybe I misunderstood).
"A very minute amount of lateral force would be applied to the stylus...". As mentioned before, no more than 5 Milligrams will ever deflect the cantilever(the arm's lateral movement is critically damped), the actual figure in operation(tracing a regular track) is quite a bit lower. The behaviour in this "domain" of any arm/cartridge combination can be checked with a Namiki side force checker or a strain gauge cartridge with appropriate analyzing circuitry.
Greetings from a believer in the KISS principle,
Frank
Please don't get me wrong. I'm fully aware of the neccessity to implement an offset angle to keep tracing error related distorsions as low as possible. That related math is 50years and older. What remains is that any correction mechanism, aka "antiskate" will preload the cantilever in the horizontal plane, on some unipivots a much smaller vertical component exists as well. An excursion in one direction, say right, will require more force than one in the opposite direction. Similar to a speaker/driver with an asymmetrical suspension characteristic(essentially all cone drivers).
There simply is(almost) no way to compensate for the skating force at the stylus tip.
What you describe regarding turning my arm into an "active" device is covered in the patent application. It complicates matters, leads to the old "error before correction" problem or requires some very clever correction algorythm, but, most importantly, sounds no more transparent.
"The key is that whatever the orientation of the headshell/stylus tip at the initial state was, it should remain in that state. " Yes.
"This could be accomplished by allowing only vertical travel of the arm, while the base provides the rotation." No(or maybe I misunderstood).
"A very minute amount of lateral force would be applied to the stylus...". As mentioned before, no more than 5 Milligrams will ever deflect the cantilever(the arm's lateral movement is critically damped), the actual figure in operation(tracing a regular track) is quite a bit lower. The behaviour in this "domain" of any arm/cartridge combination can be checked with a Namiki side force checker or a strain gauge cartridge with appropriate analyzing circuitry.
Greetings from a believer in the KISS principle,
Frank
Oh. talking about why instead of how is not necessary out of topic ?
As i had designed in the 70th a very similar (i presume) prototype of tangential arm (on the principle) to your, i believe we lie on the same planet ?
Well, no angle errors, no parasitic lateral forces on the cartridge is all about.
Purely mechanical or electronically assisted is just a question of price/results/simplicity, industrial facilities, personal preferences, agree ?
After that, resonances (acoustic or mechanical), inertia, quality of the cartridge, all that makes the real sonic difference, you are right...
On my side, about cartridges, i'm more aware about good tracking on high level trebles than response curve linearity. I too appreciated some moving coils, too expensive nowadays (300$ for a 310MC ?) , i stay with my old poor ADC to copy old vinyls to my HDs, with as much pressure in the groove it can afford...
Oh, one thing, one of the most annoying parasitic force on the cantilever is often the one of the signal wires. Linear tracking systems are the best on that matter, as the angle of the pivot does not varies, so no torsion.
Cheers,
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The RS Labs arm has NOTHING to do with keeping tangency. It is designed to reduce skating force. I don't know how many times this error has been repeated. In fact, the designer of the RS arm never claim that as the intention of the design.
rotating headshell or headshell with offset angle has more skating force.
The problem is high horizontal mass on those passive linear trackers or arms on rollers.
.
Hi Frank. Thanks for chiming in. I look forward to seeing more pictures, particularly the guiding mechanism.
.
"Oh, one thing, one of the most annoying parasitic force on the cantilever is often the one of the signal wires. Linear tracking systems are the best on that matter, as the angle of the pivot does not varies, so no torsion."
May be it is a bit off topic, however I would agree, and I also unable to understand, why on many modern expensive arms/tables we may see extremely rigid tone arm wires, sticking up (not hanging down)? They should implement said "parasitic" forces, measured in a couple of grams, and far not in just milligrams...What is a sense of applying highly sophisticated arm bearings e.t.c. together with such brutal wires?
Quote:
Originally Posted by Nanook
If a tangential arm with effectively zero error is wanted, then a passive linear tracker may be the only "true" solution (like the Souther and the Rauna Cantus).
Directdriver:
The problem is high horizontal mass on those passive linear trackers or arms on rollers.
.[/QUOTE] Also there is no level fulcrum (on true linear trackers), able of multiplying the torque, applied on pivot. As it does on both pivoting arms and semi-linear arms, helping to deal with high mass of the arm base and counterweight. So there is no gain in force (on linear trackers), and both stylus and cantilever must drag all the arm+base+counterweight masses linear way. Looks a bit scary and not very optimistic for me...
Originally Posted by Nanook
If a tangential arm with effectively zero error is wanted, then a passive linear tracker may be the only "true" solution (like the Souther and the Rauna Cantus).
Directdriver:
The problem is high horizontal mass on those passive linear trackers or arms on rollers.
.[/QUOTE] Also there is no level fulcrum (on true linear trackers), able of multiplying the torque, applied on pivot. As it does on both pivoting arms and semi-linear arms, helping to deal with high mass of the arm base and counterweight. So there is no gain in force (on linear trackers), and both stylus and cantilever must drag all the arm+base+counterweight masses linear way. Looks a bit scary and not very optimistic for me...
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I remember the first arm i designed. With a very low masse thin aluminium tube and a Euphonics head (very light too). The wires were repaced by four nickel needles plunging in 4 quater of circle baths of mercury around the axe.
(Mercury, dangerous for the health, can be replaced todays with galium alloys).
I was able to read at 45RPM a fully excentred jukebox record, with a cigarette under one side.
Try to do this with wires and heavy heads ;-)
(Mercury, dangerous for the health, can be replaced todays with galium alloys).
I was able to read at 45RPM a fully excentred jukebox record, with a cigarette under one side.
Try to do this with wires and heavy heads ;-)
Another interesting patented design that features no offset angle at the headshell and pivoting at the base but notice the curious guiding mechanism and then, just for fun, compare the arm to the Schroeder LT arm.
This one is designed by Dwipendra N. Guha, an inventor from Calcutta, India.
Tangential tracking tonearm Patent# 4153256
This one is designed by Dwipendra N. Guha, an inventor from Calcutta, India.
Tangential tracking tonearm Patent# 4153256
An externally hosted image should be here but it was not working when we last tested it.
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If you applied a torque to the arm 52 acting CCW around pivot 48 and of magnitude sufficient to counteract the stylus reaction force, the arm would no longer skate. Since the torque required varies strongly with arm position, this is not trivial.
You might also need to add a small torque acting CCW around the pivot 32 in order to keep the guide arm 44 in contact with the guide 40.
You might also need to add a small torque acting CCW around the pivot 32 in order to keep the guide arm 44 in contact with the guide 40.
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Hi guys,
Ralf and Mark hit the nail on the head. The pictured patent would be a nightmare in operation. A small preload on the guide bar 44 against the guide rail 42(I guess the number 40 relates to the actual surface aka eff. radius) is a MUST, otherwise a "perfect" skating force compensation(impossible anyway due to varying stylus drag) as suggested by Mark would have the entire arm assembly bouncing around(44 against 42). Once there is physical contact between 44 and 42, a skating force is present, which, admittedly, could be kept very small.
Now if the arm's subassembly(48,52,54,56...)was driven cw around 50 by a small motor everytime 44 lost contact with 42, the whole thing would work. But, ough, what happens if the record is eccentric... the poor cantilever would be forced towards the outer rim of the record periodically.
Easy to modify the design to avoid that...
In its stock form, such an arm would have a rather high lateral eff. mass. The counterweight 56 has to counterbalance the entire arm/bearing assembly!
I shall read the patent later again. For now, I'll commence the preparation for my birthday party tomorrow
Merry x-mas everyone!
Frank
Ralf and Mark hit the nail on the head. The pictured patent would be a nightmare in operation. A small preload on the guide bar 44 against the guide rail 42(I guess the number 40 relates to the actual surface aka eff. radius) is a MUST, otherwise a "perfect" skating force compensation(impossible anyway due to varying stylus drag) as suggested by Mark would have the entire arm assembly bouncing around(44 against 42). Once there is physical contact between 44 and 42, a skating force is present, which, admittedly, could be kept very small.
Now if the arm's subassembly(48,52,54,56...)was driven cw around 50 by a small motor everytime 44 lost contact with 42, the whole thing would work. But, ough, what happens if the record is eccentric... the poor cantilever would be forced towards the outer rim of the record periodically.
Easy to modify the design to avoid that...
In its stock form, such an arm would have a rather high lateral eff. mass. The counterweight 56 has to counterbalance the entire arm/bearing assembly!
I shall read the patent later again. For now, I'll commence the preparation for my birthday party tomorrow
Merry x-mas everyone!
Frank
Happy to see three talented designers, Ralf, Mark, and Frank, on here to discuss a weird arm.
I have a question. If I draw a line along arm "24" and extends all the way to the back will every position converge to a point that is similar to Point "B" in the Birch arm? (Reference back to post# 195 & 236)
I see the Guha arm as a variation of the Birch design with a curious guiding mechanism. Any comment?
Happy holidays to everyone!
Happy birthday to Frank!! Enjoy the party and don't let these patents get in the way of fun! :-D
I have a question. If I draw a line along arm "24" and extends all the way to the back will every position converge to a point that is similar to Point "B" in the Birch arm? (Reference back to post# 195 & 236)
I see the Guha arm as a variation of the Birch design with a curious guiding mechanism. Any comment?
Happy holidays to everyone!
Happy birthday to Frank!! Enjoy the party and don't let these patents get in the way of fun! :-D
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A glimpse of the guiding mechanism from the back of the arm. Check out that black looking piece underneath the gray plate and it is in line or parallel with the arm and would pivot along with the arm as well.
Happy New Year!
DIY Lives in 2012!
An externally hosted image should be here but it was not working when we last tested it.
Happy New Year!
DIY Lives in 2012!
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Here's something different, at least compare to the kind of tonearm we discussed on this thread. It's a motorized servo tonearm using ultra precise linear motion bearings and tracks. The below website and write up are from the company that makes the linear tracks, not the turntable company. The whole assembly looks like some military weapon!
Original German website
Website translated to English
Original German website
Website translated to English
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Most Expensive Turntable and Tonearm in the World!
From the turntable company.
Original German website
Website translated to English
.
From the turntable company.
Original German website
Website translated to English
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
.
"The most expensive record deck in the world"
Here's an English site with better translation:
"The most expensive record deck in the world" ...........and it will cost you 500,000 Euros! Talk about all out assault.
Here's an English site with better translation:
"The most expensive record deck in the world" ...........and it will cost you 500,000 Euros! Talk about all out assault.
An externally hosted image should be here but it was not working when we last tested it.
You would think for that kind of money, the designer would address the issue of eccentric records and make some kind of mechanism to center the record a la Nakamichi, consider it has so many laser systems all over the place. Wouldn't that be cheaper to address that first so the laser doesn't have to work so hard to correct the arm just to track the eccentricity of a record, consider so much money is spend on laser detecting system and linear motion tracks, etc... A little too Rube Goldberg for my taste.
The arm is intimidatingly complex but the turntable itself, based on the pictures and description, looks more conventional that's belt-driven with dual motors and hall sensors and heavy platter on magnetic bearing.
The arm is intimidatingly complex but the turntable itself, based on the pictures and description, looks more conventional that's belt-driven with dual motors and hall sensors and heavy platter on magnetic bearing.