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Old 28th May 2020, 06:26 AM   #3681
nocdplz is offline nocdplz
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Found accidentally this video

YouTube
where you can see the cantilever -despite marked warps and eccentricity- following the groove without any visible bending, while the short arm sweetly supports every movement. Strange that the carriage instead remains completely stopped, jumping forward only occasionally. (eg 1.00 - 1.40).
This is not a linear, this is a small pivoted one mounted on a mobile base.
The problem is that those active LTAs, active were not at all; they were passive arms with active correction (sensor+servo) of the errors; movements that, even if small, are in any case higher by some orders than those generating the signal. And the stop & go movement that characterizes their behavior involves accelerations that inevitably reverberate on the tracking, due the induced resonances, and more.
This is why perhaps it's not entirely stupid our research for passive solutions to the numerous problems posed by an arm without any offset .
For the rest I agree with terenceng- it is a pity that the serious companies, capable of doing true research, abandoned it at the wrong time, when the results were not yet adequate. Unfortunately many love technology much more than the music it should reproduce.

carlo

Last edited by nocdplz; 28th May 2020 at 06:29 AM.
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Old 28th May 2020, 07:29 AM   #3682
terenceng is offline terenceng  Malaysia
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Quote:
Originally Posted by warrjon View Post
The EPA100 also has VTA on the fly and dynamic damping, all lacking in high end Rega arm
Good to hear that. but I don't think the EPA100 is a real time "dynamic" damping. Looking through the brochure downloaded from vinylengine. I believe they meant they have a knob where you can adjust the magnet to adjust how much damping you need for high to low compliance cartridges. It was also released circa 1979. Same time Sony released the first biotracer arm PS-B80 and the second manufacturer to release something of similar was Victor. I don't seem to recall Technics having anything of similar. I may be wrong.



Quote:
Originally Posted by nocdplz View Post
This is not a linear, this is a small pivoted one mounted on a mobile base.
I agree they are non-exactly-perfectly-linear, but a pivoted mounted on a mobile base. Arguably this would mean a certain amount of tracking error compared to real linear trackers.

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Originally Posted by nocdplz View Post
movements that, even if small, are in any case higher by some orders than those generating the signal. And the stop & go movement that characterizes their behavior involves accelerations that inevitably reverberate on the tracking, due the induced resonances, and more.
Yes I can understand where you are coming from. I think the aftereffects of these can be categorized into

1) the friction from the stop and go movement (which may be not present, as I think they utilize magnets, so no coulomb friction)

2) the inertia energy from the go movement & vibrations from the stop (which also may not be true as this is assuming the electrical damping isn't working? and it may not be reasonable to assume so, otherwise the turntable wouldn't not be tracking an off-centered/warped record that well)

I guess the only real way to tell is if there's someone capable of measuring these guys?


Quote:
Originally Posted by nocdplz View Post
This is why perhaps it's not entirely stupid our research for passive solutions to the numerous problems posed by an arm without any offset .
Haha I wouldn't go as far as to call the research for passive solutions as stupid , but I am merely curious as to the reason for looking into passive solutions now, after passing the era of active solutions.

Meaning to say, is this an evolution from active solutions? (if yes, then what's the problem with active solutions? Or perhaps there was never a passive solution for LTA in the past? But if we look at pivot designs, the evolution was from passive -> passive with liquid damping -> active -> and now back to passive with liquid damping.)

OR

is it because current commercial tonearm manufacturers have no way to figure out how did sony/victor/denon programmed the microprocessors for their active tonearms?

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Originally Posted by nocdplz View Post
Unfortunately many love technology much more than the music it should reproduce.
I think I love both and I don't think they're both mutually exclusive

But in this context, I think there are some of us that would just love to see how science backs up what we hear (or may not be able to hear).

Cheers
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Old 28th May 2020, 10:29 PM   #3683
diyrayk is offline diyrayk  United States
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It looks like Straight Tracker and I are the only advocates of active servo linear tracking arms here on diyaudio, so I will take my turn and wave the banner in defense of the technology. The YouTube video brings up several points.

Quote:
Originally Posted by nocdplz View Post
Found accidentally this video

YouTube
where you can see the cantilever -despite marked warps and eccentricity- following the groove without any visible bending, while the short arm sweetly supports every movement. Strange that the carriage instead remains completely stopped, jumping forward only occasionally. (eg 1.00 - 1.40).
This is not a linear, this is a small pivoted one mounted on a mobile base.

carlo
The video does indeed show that that particular LT arm demonstrates a millimeter or two of stiction in the carriage movement as it corrects for tracking error. You duly note that the arm pivots freely on the carriage and the cantilever shows no visible bending in spite of the carriage stiction. You then go on to proclaim that this arm is therefore “not a linear” and imply that all active servo LT arms do the same as a genre and that they are not “LT’s” at all. You are painting with a broad brush to imply that the observed behavior of that particular specimen of a LT arm taints the whole technology. I submit that there are active servo LT’s, commercially manufactured and DIY Rabco SL8E Photoelectric Servo Control Retrofit, that do not exhibit stiction and operate with imperceptible error correction. Since this is a diy forum I think it somewhat unfair to cite an example of a commercial product, that is likely in need of maintenance or is out of adjustment, as a comparative standard by which to discount the validity of active servo technology as worthy of DIY efforts. And, by your own observation, the stiction didn’t impair the function of the stylus. I will put some numbers on that example. Let’s say the carriage stiction on the arm in the video caused a hysteresis of 2mm in the carriage movement, and the stylus to pivot length is 6 inches (152mm). This will introduce an angular deviation of 0.75 degrees. None of the carriage stiction shows up as a side-thrust on the cantilever and so there is no impairment of the tracking ability of the cartridge. For a comparable 0.75 degrees of angular error caused by deflection of, say, a 9.5mm cantilever due to stiction in a mechanical LT, it takes only 0.125mm of stiction induced hysteresis of the carriage movement to cause the same tracking error as 2mm of stiction in the servo LT. 0.125mm of cantilever deflection is barely visible at all, and the stiction in a mechanical linear all gets directly applied as a side thrust.

Quote:
Originally Posted by nocdplz View Post
The problem is that those active LTAs, active were not at all; they were passive arms with active correction (sensor+servo) of the errors; movements that, even if small, are in any case higher by some orders than those generating the signal. And the stop & go movement that characterizes their behavior involves accelerations that inevitably reverberate on the tracking, due the induced resonances, and more.

carlo
Your argument that the “movements” of the servo are greater than the generated signal is verbal sleight of hand. The error deviations in a servo, 2mm in our example, do not cause cantilever deflection and do not get applied to the few millivolts of signal coming from the cartridge, except as an angular error effect on the waveform. If anything, the cantilever deflection caused by stiction in a mechanical will cause uneven pressure on the groove wall, likely push the suspension towards a nonlinear region of it’s operating range and cause angular error anyway. The “stop and go” movement takes place at the carriage and pivot end of the arm, the video demonstrates that the cantilever is unstressed. As can be seen in the video, there are no accelerations ‘reverberating’ on the tracking or induced resonances. This thread already has posts with links to YouTube videos of mechanical linears, commercial products and DIY, that show very noticeable cantilever deflection. I submit that a less-than-perfect mechanical linear is far worse than a less-than-perfect active servo linear if we look at all the combined foibles of each design technology.

Air bearing LT’s are, well, another thing with their own set of foibles. I’m going to let that sleeping dog lie.

Quote:
Originally Posted by nocdplz View Post

This is why perhaps it's not entirely stupid our research for passive solutions to the numerous problems posed by an arm without any offset .

carlo
Did I or any other proponent of active servo LT’s ever say research for passive solutions was ‘stupid’? Why the negative energy towards active linear solutions? IMO there is an ultimate DIY example of mechanical LT technology and an ultimate DIY example of air bearing LT technology here on diyaudio – you guys know who you are.

Ray K
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Old 28th May 2020, 10:40 PM   #3684
warrjon is offline warrjon  Australia
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Quote:
Originally Posted by diyrayk View Post
Did I or any other proponent of active servo LT’s ever say research for passive solutions was ‘stupid’? Why the negative energy towards active linear solutions? IMO there is an ultimate DIY example of mechanical LT technology and an ultimate DIY example of air bearing LT technology here on diyaudio – you guys know who you are.

Ray K

Just remember that Carlo's first language is not English. I don't think it's negative energy just translation.
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Old 29th May 2020, 07:51 AM   #3685
nocdplz is offline nocdplz
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Hi Terenceng, hi Ray,
sorry if my English (thanks, lawyer :-) does not show the ironic tone of my provocation: it's me, not others, who - after ten years of tests and efforts on TA of various types - often wonder if it is not stupid to continue an exploration completely out of time.
Despite our passion, and even despite the strange revival of these years, vinyl has objectively no future. Just like the film, with which I've worked my whole life with the utmost dedication (this instead is just a toy for a retired)
It does not have it because, rightly, the technology more than 30 years ago took a completely different path, whose validity is consolidating more and more in an incontrovertible way. This is the reason why large companies, together with their customers, have abandoned vinyl: the HiFI market focuses much more on technology and its narration, than to the music reproduction.
We can rightly complain it - I think the same as Terenceeng - but this is the reality, nobody will invest large capacity and money in a dead end.

Now lets go back to that video: I have not at all contested the value of that realization, which behaves very well to my eyes, i'm just contesting that could be defined as a linear one. Geometrically it is not.
And as far as I understand of the tonearms in general, I doubt that the fact that the base stops and goes (with fast movements of fractions of millimeter, compared to the microns of the stylus to induce the electric signal) does not affect the signal itself. (resonances are not visible in any video, probably). This would inevitably happen if the arm was rigidly connected to the carriage; this hybrid solution is perhaps a smart way to avoid it.
The only active realization that convinces me (geometrically) is the revolutionary one invented by Ralf, who instead is a true linear. (cartridge horizontal movements are linear)*.

carlo
By the way, to be fundamentalist, the only working realization really linear I know, (both on the horizontal+vertical plane) is my Lil Casey...

Last edited by nocdplz; 29th May 2020 at 08:10 AM.
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