I would expect the velocity of the stylus towards the center hole will vary far beyond any constant velocity stylus movement assembly, making the tip bend too far to either side.
I've used 33's that had one song, 5 minutes, one side, with major modulation and groove spacing to accomodate.
And, in between tracks, spacing is large..
Off center holes also.
John
I've used 33's that had one song, 5 minutes, one side, with major modulation and groove spacing to accomodate.
And, in between tracks, spacing is large..
Off center holes also.
John
Hi,
With a highly compliant cantilever as the one fitted to the Shure V15 it's not even important: those types of carts hardly throw any energy back into the tonearm....
Low compliance MCs are quite a different story and this is where tonearm design really comes to its' own.
Want to know what your tonearm's worth in that department?
Fit a Decca, you'll know when the sound starts to break up.
BTW, it makes my skin curl when people seem to think it's the cartridge making the movements: it's the arm following whatever's the grooves' pitch is on that record.
Newtons' law on action and reaction gets you a long way to understanding analogue playback very much in the same way Ohms' law does for electronics.
Cheers,
With a highly compliant cantilever as the one fitted to the Shure V15 it's not even important: those types of carts hardly throw any energy back into the tonearm....
Low compliance MCs are quite a different story and this is where tonearm design really comes to its' own.
Want to know what your tonearm's worth in that department?
Fit a Decca, you'll know when the sound starts to break up.
BTW, it makes my skin curl when people seem to think it's the cartridge making the movements: it's the arm following whatever's the grooves' pitch is on that record.
Newtons' law on action and reaction gets you a long way to understanding analogue playback very much in the same way Ohms' law does for electronics.
Cheers,
fdegrove said:Hi,
With a highly compliant cantilever as the one fitted to the Shure V15 it's not even important: those types of carts hardly throw any energy back into the tonearm....
Low compliance MCs are quite a different story and this is where tonearm design really comes to its' own.
Want to know what your tonearm's worth in that department?
Fit a Decca, you'll know when the sound starts to break up.
BTW, it makes my skin curl when people seem to think it's the cartridge making the movements: it's the arm following whatever's the grooves' pitch is on that record.
Newtons' law on action and reaction gets you a long way to understanding analogue playback very much in the same way Ohms' law does for electronics.
Cheers,
what are you talking about ?
statement 1 is entirely incorrect.
statement 2 is just as bad as compliance per se does not transfer energy.
statement 3 has some basis, the Decca is a difficult cartridge.
statement 4 is just inane.
statement 5 is just wrong.
I'm not going to explain all these points because they don't deserve it.
sreten.
I am talking about a constantly laterally acclerating motor based on the angular velocity and starting position of the stylus. LPs were known as constant velocity recordings, but they were referring to angular velocity. So if we have a constantly accelerating motor (with respect to angular velocity, time and start position), it will be accelerating constantly with the stylus, and won't it stay parallel? Dont just answer no, explain with physics, I'm trying to understand the physics here!
I do listen to your howls regarding program material and cutting depth, but since you refrenced Newton, Newton says it shouldnt matter at low speeds, even more so at low masses, even more so with kinetic friction of moving objects, which is a fraction of static coefficient of friction. Those forces are being applied at an angle to the stylus, and I have those equations too, also. they are distributed rather evenly with respect to both sides of the stylus, one is lateral I believe and the other depth, so the lateral side (which is it? ) is providing our lateral inward push so to speak.
We have control over where the stylus starts, so we can choose a start point. This gives us a lot of info. We pick a start point with known radius, start time and angular velocity, from which we can also determine the centripital force vector, dependent on radius and mass of arm at that point. Slightly adjusting for stylus friction, we can obtain an equation of a polynomial, the integral of which with respect to time should give position. Using this we can calculate accleration and start velocity. The law of motion in one dimention is this: given position y of the stylus at time t , the derivative of position is velocity....v=dy/dt...derivative of velocity is acceleration a=dv/dt. this is the intantaneous acceleration. This only works if the average velocity is a linear function with respect to time, and I believe it is, because the acceleration is linearly proportional to the square of the radius, so by default, its linear.
So we know the angular velocity and position, giving us the starting velocity of our arm, and we already have the average velocity (if FDE was correct) whose derivative is the instantaneuos acceleration, the rate of acceleration of our arm. For all intensive purposes, our arm will appear to be at constant velocity, except it will be constantly slightly accelerating based on the position the stylus should be at respective to time. Now the problem that has been raised is what if it overruns or lags due to program material.?
Now, you make a great deal about friction, but kinetic friction between moving bodies is almost constant at low speeds. That is why I wanted to know the coefficient of friction, because this can be factored into a more exact equation, a polynomial equation factoring in the average kinetic friction. This will give us a +_error to set our acceleration between, and maybe to adjust on a record to record basis, but only slightly. You audiophiles love to tweak, this will be a joy, different tweak on each record. Just kidding.
Although it varies over time, there exists an average friction, just like and average velocity. Since it is linear, we can use the average for the instantaneous, and calculate the +/- forces to skip and to lag. And given this average over the entire program material, the arm can only be more accurate than a pivot if the motor is placed between these error factors to start with. In fact, the last song, which traditonally has the worst tracking error, would in theory have the best performance with this arm, as the arm should statistically get better with more time played, as the instantaneous variations in values more closely approach the averages.
Taking the force vector normal to the stylus, we can solve for the maximum speed before the stylus jumps the groove at its "slippriest point and maximum angle, and at its highest drag. We can take the derivative of the fastest speed to limit the acceleration of the motor to high and low, and set the acceleration inbetween these two limits. Hopefully, neither will be exceeded before program material ends. The problem with this method is it depends on the mass of the cartridge. This is why I wanted to design for a specific cartridge, to keep that factor in the forces on the stylus constant.
The great question is if the graph of velocity as a funtion of time is a straight line or near it. I believe it is over the vast majority of records, or they would sound very funny. I think over the limited arc of a 33 1/3 record it is, and if the constant acceleration is set up right, one will end the record before the arm outruns or lags the stylus. The benefits of better tracking would outweight the few times this error would occur. Comments? It is given that these equations only work if I can calculate an average velocity. But remember that Keppler and Newton found these equations to work with planets, which are far larger and faster than LP's And that is where your many comments about record variation may have some merit, but those are anecdotal observations, not empirical. I want to know the force vecors acting on the arm. The velocity we are referring to is solved for by the equation for centripital force Fc= mv2/r where v2/r is the centripital acceleration. given position y of the stylus at time t , the derivative of position is velocity....v=dy/dt...derivative of velocity is acceleration a=dv/dt. this is the intantaneous acceleration.
I now believe the gaps between songs are a bigger problem than the kinetic friction. The lack of friction will introduce more errors than program material. Are those gaps standardized? Here is the argument that friction varies so much. If the modulation was such a problem, your records would have lots of WOW before the average velocity varied so much from record to record, and you would notice it. Or they would skip. For all intensive purposes, we can hold the coefficient of friction constant.
I'll finish this later. You guys have got a great discussion going on now. Thanks for getting back on topic. You too, FDE, even if you need to go back to your physics book, you're trying to be constructive.
I do listen to your howls regarding program material and cutting depth, but since you refrenced Newton, Newton says it shouldnt matter at low speeds, even more so at low masses, even more so with kinetic friction of moving objects, which is a fraction of static coefficient of friction. Those forces are being applied at an angle to the stylus, and I have those equations too, also. they are distributed rather evenly with respect to both sides of the stylus, one is lateral I believe and the other depth, so the lateral side (which is it? ) is providing our lateral inward push so to speak.
We have control over where the stylus starts, so we can choose a start point. This gives us a lot of info. We pick a start point with known radius, start time and angular velocity, from which we can also determine the centripital force vector, dependent on radius and mass of arm at that point. Slightly adjusting for stylus friction, we can obtain an equation of a polynomial, the integral of which with respect to time should give position. Using this we can calculate accleration and start velocity. The law of motion in one dimention is this: given position y of the stylus at time t , the derivative of position is velocity....v=dy/dt...derivative of velocity is acceleration a=dv/dt. this is the intantaneous acceleration. This only works if the average velocity is a linear function with respect to time, and I believe it is, because the acceleration is linearly proportional to the square of the radius, so by default, its linear.
So we know the angular velocity and position, giving us the starting velocity of our arm, and we already have the average velocity (if FDE was correct) whose derivative is the instantaneuos acceleration, the rate of acceleration of our arm. For all intensive purposes, our arm will appear to be at constant velocity, except it will be constantly slightly accelerating based on the position the stylus should be at respective to time. Now the problem that has been raised is what if it overruns or lags due to program material.?
Now, you make a great deal about friction, but kinetic friction between moving bodies is almost constant at low speeds. That is why I wanted to know the coefficient of friction, because this can be factored into a more exact equation, a polynomial equation factoring in the average kinetic friction. This will give us a +_error to set our acceleration between, and maybe to adjust on a record to record basis, but only slightly. You audiophiles love to tweak, this will be a joy, different tweak on each record. Just kidding.
Although it varies over time, there exists an average friction, just like and average velocity. Since it is linear, we can use the average for the instantaneous, and calculate the +/- forces to skip and to lag. And given this average over the entire program material, the arm can only be more accurate than a pivot if the motor is placed between these error factors to start with. In fact, the last song, which traditonally has the worst tracking error, would in theory have the best performance with this arm, as the arm should statistically get better with more time played, as the instantaneous variations in values more closely approach the averages.
Taking the force vector normal to the stylus, we can solve for the maximum speed before the stylus jumps the groove at its "slippriest point and maximum angle, and at its highest drag. We can take the derivative of the fastest speed to limit the acceleration of the motor to high and low, and set the acceleration inbetween these two limits. Hopefully, neither will be exceeded before program material ends. The problem with this method is it depends on the mass of the cartridge. This is why I wanted to design for a specific cartridge, to keep that factor in the forces on the stylus constant.
The great question is if the graph of velocity as a funtion of time is a straight line or near it. I believe it is over the vast majority of records, or they would sound very funny. I think over the limited arc of a 33 1/3 record it is, and if the constant acceleration is set up right, one will end the record before the arm outruns or lags the stylus. The benefits of better tracking would outweight the few times this error would occur. Comments? It is given that these equations only work if I can calculate an average velocity. But remember that Keppler and Newton found these equations to work with planets, which are far larger and faster than LP's
And that is where your many comments about record variation may have some merit, but those are anecdotal observations, not empirical. I want to know the force vecors acting on the arm. The velocity we are referring to is solved for by the equation for centripital force Fc= mv2/r where v2/r is the centripital acceleration. given position y of the stylus at time t , the derivative of position is velocity....v=dy/dt...derivative of velocity is acceleration a=dv/dt. this is the intantaneous acceleration. I now believe the gaps between songs are a bigger problem than the kinetic friction. The lack of friction will introduce more errors than program material. Are those gaps standardized? Here is the argument that friction varies so much. If the modulation was such a problem, your records would have lots of WOW before the average velocity varied so much from record to record, and you would notice it. Or they would skip. For all intensive purposes, we can hold the coefficient of friction constant.
I'll finish this later. You guys have got a great discussion going on now. Thanks for getting back on topic. You too, FDE, even if you need to go back to your physics book, you're trying to be constructive.
I'm giving up.
There has been a time -long ago- when there were constant velocity recordings. BUT THIS REFERRED TO THE MODULATION OF THE GROOVE! Not the spacing of the grooves.
If you start from wrong premises you end up nowhere.
Frank, can you cut all those wise-cracks and explain for everybody whatever you are talking about? If you don't like to be adressed as a troll, you better explain or shut up. If you know what you are talking about and then share your knowledge -as supposed on a forum- but stop implying that everybody is an idiot.
There has been a time -long ago- when there were constant velocity recordings. BUT THIS REFERRED TO THE MODULATION OF THE GROOVE! Not the spacing of the grooves.
If you start from wrong premises you end up nowhere.
Frank, can you cut all those wise-cracks and explain for everybody whatever you are talking about? If you don't like to be adressed as a troll, you better explain or shut up. If you know what you are talking about and then share your knowledge -as supposed on a forum- but stop implying that everybody is an idiot.
It's obvious that it isn't possible to track a record with an arm moving constantly inward, even at a rate related to the distance from the inner groove.
'perfusionist' could estimate how large an error between the arm position and the stylus can be allowed to build up before performance suffers, and how much the cutter might vary the groove pitch during loud passages.
We would have to preplay each record with a measuring device to determine how to drive our pickup arm. At the moment I'm not seeing the benefit...
By contrast the physics that allows a conventional radial pickup to produce output yet move inwards with the groove and track warps and eccentricity without generating significant output would appear quite approachable.
Paul
'perfusionist' could estimate how large an error between the arm position and the stylus can be allowed to build up before performance suffers, and how much the cutter might vary the groove pitch during loud passages.
We would have to preplay each record with a measuring device to determine how to drive our pickup arm. At the moment I'm not seeing the benefit...
By contrast the physics that allows a conventional radial pickup to produce output yet move inwards with the groove and track warps and eccentricity without generating significant output would appear quite approachable.
Paul
perfusionist :
I'm giving up on you.
You seem to not want listen or be interested in any salient fact
that inconveniently does not suit your way of seeing things.
And when needed conveneniently make up assumptions that
are wrong justified by incoherent arguements, as the assumptions
are wrong so are the arguements.
Consequently your rambling musings compound one error
after another, you don't seem to care they do not make any
practical sense whatsoever.
I wouldn't let you fix my car........Or get into a car you built.
Frank :
a) Having the correct arm resonant frequency is important,
especially for suspended subschassis turntables.
b) high complinance cartridges with low tip mass still throw a large
amount of energy back into the arm, only a few dB less than a
good moving coil.
Not in my experience. the type of cartridge does not matter.
Effective tip mass and generator damping seem to be more
important issues.
Which illustrates my point above.
Assuming the cartridge is bolted to arm what diiference does it make ?
I simply disagree with this as its far too simplistic.
Transmission line theory helps a lot IMO.
sreten.
I'm giving up on you.
You seem to not want listen or be interested in any salient fact
that inconveniently does not suit your way of seeing things.
And when needed conveneniently make up assumptions that
are wrong justified by incoherent arguements, as the assumptions
are wrong so are the arguements.
Consequently your rambling musings compound one error
after another, you don't seem to care they do not make any
practical sense whatsoever.
I wouldn't let you fix my car........Or get into a car you built.
Frank :
a) Having the correct arm resonant frequency is important,
especially for suspended subschassis turntables.
b) high complinance cartridges with low tip mass still throw a large
amount of energy back into the arm, only a few dB less than a
good moving coil.
Not in my experience. the type of cartridge does not matter.
Effective tip mass and generator damping seem to be more
important issues.
Which illustrates my point above.
Assuming the cartridge is bolted to arm what diiference does it make ?
I simply disagree with this as its far too simplistic.
Transmission line theory helps a lot IMO.
sreten.
Hi,
For high compliance suspensions such as used by Shure it isn't critical.
You can compare them to the suspension of a typical American automobile if you like.
What does the TT suspension have to do with tonearm resonance?
Almost any MM cartridge will have a tip mass that's much higher than modern MCs.
The cantilevers are more often than not very crude affairs that are basically preformed hollow pipes with a flattened end where the diamond is pressfit.
See above.
Why?
If you know that a Decca cart. hardly has any cantilever to speak of and that it's mounted nearly vertically and hardly has any suspension at all, you'll realise the amount of energy that's thrown back into the arm and cartridge body.
Any Decca owner will confirm that.
The difference is that when we discuss tonearms it's confusing to follow what's meant when people add catridges into the equation.
Which is why no tonearm designer I know off will refer to catridge movements when explaning his design rationale.
Of course it is but people have to start somewhere...
Sure does, as does a number of other items such propagation of soundwaves in various materials...
Anyway, let's return to linear trackers before we have to start yet another thread on TT and tonearm design...
Cheers,
For high compliance suspensions such as used by Shure it isn't critical.
You can compare them to the suspension of a typical American automobile if you like.
What does the TT suspension have to do with tonearm resonance?
Almost any MM cartridge will have a tip mass that's much higher than modern MCs.
The cantilevers are more often than not very crude affairs that are basically preformed hollow pipes with a flattened end where the diamond is pressfit.
See above.
Why?
If you know that a Decca cart. hardly has any cantilever to speak of and that it's mounted nearly vertically and hardly has any suspension at all, you'll realise the amount of energy that's thrown back into the arm and cartridge body.
Any Decca owner will confirm that.
The difference is that when we discuss tonearms it's confusing to follow what's meant when people add catridges into the equation.
Which is why no tonearm designer I know off will refer to catridge movements when explaning his design rationale.
Of course it is but people have to start somewhere...
Sure does, as does a number of other items such propagation of soundwaves in various materials...
Anyway, let's return to linear trackers before we have to start yet another thread on TT and tonearm design...
Cheers,
Hi,
Indeed it isn't possible with a motorised device moving inwards at a constant speed.
The result would be a stylus skipping the grooves as the arm moves, at best, or at worst a broken cantilever.
Other than the common airbearing designs which suffer only from a high horizontal mass, there are a few mechanical designs such as Souther (Clearaudio) and the Paragon by Nottingham Analogue.
Once setup for correct tangency they track the record exactly as it was cut.
A pivoted arm, no matter how well designed only approaches tangency at two spots on the record if you're lucky.
Cheers,
Indeed it isn't possible with a motorised device moving inwards at a constant speed.
The result would be a stylus skipping the grooves as the arm moves, at best, or at worst a broken cantilever.
Other than the common airbearing designs which suffer only from a high horizontal mass, there are a few mechanical designs such as Souther (Clearaudio) and the Paragon by Nottingham Analogue.
Once setup for correct tangency they track the record exactly as it was cut.
A pivoted arm, no matter how well designed only approaches tangency at two spots on the record if you're lucky.
Cheers,
Sreten and Havoc,
I've found your posts to be the most informative, didnt mean to turn you off. I have learned a lot from both your posts, thanks.
Probably the reason my ideas are from the old days are I did my homework, I read all the original papers on tonearms but the papers I have read are 30-50 years old, so many new ideas I'm sure you know but I dont. That's why I ask for your patience as I learn and get up to speed. I didnt realize that most air arms were not motorized, I dindnt know the stylus could pull that much mass along the track.
Given a coefficient of .3 and a cartridge compliances of 15 and 25, can anyone estimate the maximum mass, beyond which the performace of a tangential passive (non motor) air arm will suffer due to too much effective mass? We know that effective mass = actual mass in an air tangential. What would be an ideal mass?
Also, why are longer radial tonearms no longer popular, is it simply for convenience, as they track 25% better.
I've found your posts to be the most informative, didnt mean to turn you off. I have learned a lot from both your posts, thanks.
Probably the reason my ideas are from the old days are I did my homework, I read all the original papers on tonearms but the papers I have read are 30-50 years old, so many new ideas I'm sure you know but I dont. That's why I ask for your patience as I learn and get up to speed. I didnt realize that most air arms were not motorized, I dindnt know the stylus could pull that much mass along the track.
Given a coefficient of .3 and a cartridge compliances of 15 and 25, can anyone estimate the maximum mass, beyond which the performace of a tangential passive (non motor) air arm will suffer due to too much effective mass? We know that effective mass = actual mass in an air tangential. What would be an ideal mass?
Also, why are longer radial tonearms no longer popular, is it simply for convenience, as they track 25% better.
Check the Ladegaard design, if I remember well, then he added about 300g to the cart without any problems.
Don't know. Just a guess:
- mass, they are larger
- size, not everybody is charmed by a 1m arm
- setup, you need a lot of space and if you want to mount the arm onthe same base as the platter it can become a problem
- fashion, hifi is a lot about fashion, you can deny it and/or not like it, but it is that way.
Hi,
Actually the stylus isn't pulling anything, it just follows the spiral groove as it passes beneath it at the given platter speed (331/3 or 45 RPM.
The reason the 12' arms were preferred is not because they track better but that they had smaller offset error.
They're not popular with MC cartridges because their length augments their resonant frequency.
Cheers,
Actually the stylus isn't pulling anything, it just follows the spiral groove as it passes beneath it at the given platter speed (331/3 or 45 RPM.
The reason the 12' arms were preferred is not because they track better but that they had smaller offset error.
They're not popular with MC cartridges because their length augments their resonant frequency.
Cheers,
fdegrove said:Hi,
Actually the stylus isn't pulling anything, it just follows the spiral groove as it passes beneath it at the given platter speed (331/3 or 45 RPM.
The reason the 12' arms were preferred is not because they track better but that they had smaller offset error.
They're not popular with MC cartridges because their length augments their resonant frequency.
Cheers,
The question was what's the maximum horizontal mass WHATEVER force is moving it, that an air arm can carry, you know what the hell I'm asking!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.