It certainly is, that's what this thread is al about, but unfortunately I haven't still got the right idea yet how to add damping to my cartridge.
I don't understand why Shure and others ever skipped this feature.
And to Ray: using an other cartridge doesn't bring me further, because I want to keep this one.
I have thought of putting a piece of rubbersheet between Cart and Arm, maybe this could bring some damping in the vertical plane ?
Hans
As you have a linear arm it might be quite easy as your trough can be straight and you can do a Rock style front damper.
Actually I was getting the threads mixed up a little, I meant that we probably don't want competing softwares to go with the test LP. I hope we can agree on one presentation.
Also I misspoke, the radial display shows orders not Hz for wiggles that are synchronous with the LP rotation. To get Hz you have to factor in the rpm. The 9 wiggles are related to the 9:1 ratio of pulley to platter rotation.
Don't worry. I will never supply a SW program for general use.
But I can give you a number of suggestions by now, based on recent experimenting with numerous .wav files like:
1) having an option for presentation in a linear or a circular display, because a circular presentation has its limits in amplitude where a linear display does not, thereby restricting the resolution.
2) displaying 3 LP revolutions instead of 2, since IEC386 requires 5 seconds as a minimum
3) showing the averaged spectrum of the individual spectra of the 3 revolutions to have a more accurate result in amplitude, but not too fine in frequency resolution.
4) Optionally showing the averaged spectrum of the same 3 LP revolutions of the waving of the input signal, to see in how far the spectrum in 3) is affected by Cart/Arm resonance
And as a point before releasing the SW: testing whether the SW generating the IM signal, is flat up to the frequency that is displayed in the spectrum and to what frequency, 40 Hz or 100 Hz ? This can easily be tested by artificially making an FM modulated .wav file with various steps in frequency.
I will be happy to provide you with such a .wav file.
Implementing my suggestions is up to you, leave them if you don't like.
Hans
I'm already thinking of ways of using larger numbers of revolutions for looking at the spectrum. For large FM deviations the radial display is also distorted because of its projection, a switch to display either or even both at the same time is trivial.
There is an inevitable support issue, I don't want to go through what Edmond Stuart is on his distortion app.
The original Shure (not ‘SME’) brush provides some horizontal damping. Shure patented an improved version of their brush in 1985 http://www.google.com.pg/patents/US4514836 but never put it into production. In the ‘improved’ patent, Shure admits that they didn’t fully understand the horizontal damping mechanism of the brush in their original patent. The ‘improved’ patent uses a brush shaped in a circular fan like a chimney sweeper as opposed to a flat profile like a paintbrush, and claims the horizontal damping/stabilization comes from “interfiber friction” and horizontal locking with the grooves that results from the bristles assuming a ‘V’ shape as the record rotates under the circular brush. See Column 1, lines 30-40 and Column 3, lines 35-38 in the patent. The “interfiber friction” mechanism of horizontal damping in Shure’s ‘improved’ patent is remarkably similar to (OK, it’s the same thing as) the inter-strand friction mechanism of the 1928 Stockbridge damper patent that I talked about back in post #122 Turntable speed stabilty
In designing and building my own unipivot arm, I put most of the damping in the vertical direction for warp damping, and less damping in the horizontal direction, instead relying on the zero offset angle of my linear tracker to reduce FM from horizontal scrubbing.
A point worth noting, the function of Shure stabilizer is not as simple as it appears at first glance. It does provide effective vertical mode damping but, it also importantly shunts ½ grams' worth of vertical warp acceleration force around the stylus suspension. In other words, it provides damping and also removes ½ grams’ worth of warp deflection load from the stylus suspension whereas trough damping and pivot damping adds warp deflection load to the stylus suspension.
Ray K
Last edited:
I’m puzzled by your second comment about Shure skipping this feature. Shure is the only manufacturer that ever offered it. The patents have expired and other manufacturers now have no excuse for not offering it, other than having to admit that it is a good idea and they are afflicted with ‘not invented here’ syndrome.
I’m not trying to convince you to change cartridges. I merely suggested a Shure cartridge with an OEM stabilizer brush as being the ideal candidate for testing your hypothesis objectively. When you see a measurable improvement in FM stability with the brush, you might want to reconsider. My all-time favorite cartridge isn’t a Shure either, but the company stopped making cartridges altogether and I’ve moved on.
I predict a 'no' to that.
Ray K
D'oh. Must think whilst typing. There was a japanese add on damper back in the 70s whose name I cannot remember. This used pneumatic damping. It looked very nice, but is very pricey when it comes up second hand.
I agree that the shure design it wonderfully clever in the way it accomplishes so much with so little.
Was the purpose of the little brush on the Stanton cartridges the same stabilizing, or just dust cleaning?
Hi Ray,
Thanks for your contribution.
One question: How exactly did you put damping in the vert direction to your own arm ?
And about experimenting with a Shure element with damper, I'm almost sure it will reduce IM distortion, but the current level of this distortion is so far under the auditory threshold, that it would be a pure academic experiment.
That may also be the reason why manufacturers didn't proceed with this feature.
But I'm still interested in adding "some thing" to my existing Cart / Arm.
Hans
Ray,
aditionally to your Shure patent, did you ever read this patent:
Patent US4755979 - Disc reproducing system for compensating mechanical imperfections - Google Patentsuche
It is very funny, but also very sophisticated.
It measures the movement of the Cart relative to the LP and raises or lowers the platter accordingly in a closed loop system.
Hans
aditionally to your Shure patent, did you ever read this patent:
Patent US4755979 - Disc reproducing system for compensating mechanical imperfections - Google Patentsuche
It is very funny, but also very sophisticated.
It measures the movement of the Cart relative to the LP and raises or lowers the platter accordingly in a closed loop system.
Hans
I am not sure I agree with that statement. If you look at the B&K papers they definately show levels of IM that should be audible. I very nearly bought the damper for my SME309 over xmas, but £400 for two small pieces of metal, 3 screws and a plastic paddle put me off. One day I will because of some testing I want to do to check a theory.
The theory is that, modern 10-12g effective mass arms work very well with modern mid compliance MC cartridges giving 10-12Hz resonant frequency which is less audible than lower frequencies. However if I were to stick my Audio technica AT-150MLx in, which is both high mass for MM and highish compliance then it shoves the resonance down to the point where it might cause issues. It's a mismatch, and in this case damping would help. But the cost of the factory damping solution might also obtain me an arm that is better suited to the cartridge as well (or a second wand for my SIII).
But I am becoming more convinced that most MM*s are just not suited to modern arms, but 21st century vinyl lovers don't actually care as the whole market is set to tempt people to MC.
* I do have a Shure SC35 for which my arm is not massive enough as well 🙂
The theory is that, modern 10-12g effective mass arms work very well with modern mid compliance MC cartridges giving 10-12Hz resonant frequency which is less audible than lower frequencies. However if I were to stick my Audio technica AT-150MLx in, which is both high mass for MM and highish compliance then it shoves the resonance down to the point where it might cause issues. It's a mismatch, and in this case damping would help. But the cost of the factory damping solution might also obtain me an arm that is better suited to the cartridge as well (or a second wand for my SIII).
But I am becoming more convinced that most MM*s are just not suited to modern arms, but 21st century vinyl lovers don't actually care as the whole market is set to tempt people to MC.
* I do have a Shure SC35 for which my arm is not massive enough as well 🙂
In FM they typically are audible, in most untreated rigs. IIRC damping coefficient ends up between 0.08 and 0.15 naturally, which is more than a bit skinny.
Stability and eliminating audibility is all about making as much use of whatever damping there is, and topping up as necessary, IMO. Higher resonant f makes for lower Q given a set amount of damping. And that probably explains the relative success often reported from lighter arms. But selection of res f isn't really remedial. That's about damping.
MC carts tend to have more intrinsic damping, FWIW.
LD
I thought that MCs had more damping, but wasn't sure. Makes sense.
I see the damping/Fres issue as multidimensional. For me the 3 things I am trying to balance (until I find more things) are
1. Audibility (higher f is less audible all things being equal, which they rarely are)
2. Damping (higher f is easier to damp)
3. Warp excitation gets worse as you drop frequency
All of these suggest that 10-13Hz is a good target, with 13Hz being good enough for the BBC.
But taming MM on the 309 is something I want to try, but I'll need to build a damper to prove the principle before I splash out so much on the integrated solution 🙂
I see the damping/Fres issue as multidimensional. For me the 3 things I am trying to balance (until I find more things) are
1. Audibility (higher f is less audible all things being equal, which they rarely are)
2. Damping (higher f is easier to damp)
3. Warp excitation gets worse as you drop frequency
All of these suggest that 10-13Hz is a good target, with 13Hz being good enough for the BBC.
But taming MM on the 309 is something I want to try, but I'll need to build a damper to prove the principle before I splash out so much on the integrated solution 🙂
Vertical damping can be achieved by using silicone fluid at the bearing or different part of tonearm.
BTW, what software did you use to get these plots? Thanks!
Last edited:
For a linear tracking arm, it is easy. A silicone tough is the way to go. I did it.
For a pivot arm, in my opinion, it works best to put damping at bearing.