ahh OK. Thanks Jim.
I also like to think about mechanical things. It surely is fun. 🙂
How about to simplify the whole air bearing arm. (Don't know if it will work.😱) Here is the concept. instead of having bushing at the headshell we move it to air bearing base at opposite end. We make one single rigid uniform unit tonearm wand which moves horizontally on air bearing shaft which is held by two vertical air bearing at the base. Total weight of arm wand + base can be lowered by using proper material. It will isolate from external vibrations too.
Regards.
Hi Joe,
Since the upgrade to the jewelled bearings and tungsten carbide rods and wheels I haven't made any modifications but I have played a ton of records. I have recently indirectly compared my system to a couple of mega buck systems and in both cases it blew them away, which is a great confirmation that I'm doing something right. To be honest I have nearly run out of ideas on how to improve the deck without starting again from scratch. (That would probably end in divorce). I think I'm going to leave the deck as it is for now and concentrate on the rest of the system. Of course if I get a turntable brainwave I'll experiment with it and post all my findings.
Niffy
Hi Niffy,
It must be a real pleasure to discover hidden information within your vinyl collection. I bet your arm has raised more than a few eye brows but made believers of any doubters. You did a lot of the heavy lifting with your time and effort in bringing this linear arm to life. Thanks again and enjoy the fruits of your labor. Happy listening.
Joe
It must be a real pleasure to discover hidden information within your vinyl collection. I bet your arm has raised more than a few eye brows but made believers of any doubters. You did a lot of the heavy lifting with your time and effort in bringing this linear arm to life. Thanks again and enjoy the fruits of your labor. Happy listening.
Joe
Hi Joe,
My deck certainly has raised a few eyebrows, normally accompanied by the question is that a record player? or more often what is that? Often followed by do you mind if I take a photo. Quite satisfying to have something I've worked so hard on being universally appreciated.
Jim.
As always, fantastic quality of workmanship. Your latest carriage version looks very solid and well thought out. I'm right along side you in you decision to lower the rail as close to the record surface as possible (my carriage has a similar clearance above the record surface). This will minimize any possible warp wow and help to reduce tracking force variation. You probably already know my opinions on keeping the arm length nice and short. Eliminate the armtube and you eliminate armtube resonance, simple.
On the earlier discussion about effective mass.
Bearing friction is proportional to arm mass via the coefficient of friction of the bearing as you have suggested. With an air bearing the coefficient of friction is SO low that friction is effectively zero in both the vertical and lateral planes. This does NOT mean that effective masses will effectively be the same. The effective mass describes how the arm will accelerate and move for a given input force/frequency. An arm with a higher mass will move less than one with a lower mass. A higher mass will control the cartridge better but will result in a lower cantilever resonance which may cause it's own problems. I discussed this in some depth in the diy linear tonearm thread about a year ago. In my opinion the ideal effective mass is dependent upon cartridge compliance, the lowest frequency cut into the record and the highest frequency of anything that could disturb replay eg warps. As these are completely different in the vertical and horizontal planes the ideal masses will be completely different. The ideal lateral effective mass is much higher than the ideal vertical.
However making the difference between the two masses too great can cause some issues.
If you imagine a signal that is cut in only one channel. The stylus in this case will move at 45°. If the effective masses are the same the cartridge body will move a small amount vertically and the same amount laterally, also at 45° eg it will move a small amount in the same direction as the stylus.
Now imagine the lateral mass is very high. The cartridge body will still move vertically by a small amount but not laterally. The cartridge body is only moving vertically which will cause an output in both channels. This will result in a small amount of crosstalk between channels reducing channel separation. The amount of this separation will decrease at about 6dB/octave.
Records are recorded in mono below about 120hz. As long as the ratio between the two masses is kept to about 1:4 then by the time you get to 120hz the crosstalk is down to about -30dB. About as good as any cartridge can pick up. Above this frequency the separation improves rapidly.
So is this actually a problem. NO. One of the main improvement of a linear tracking tonearm over a pivoted design is the improvement in stereo imaging. Any theoretical disadvantage to having different effective masses is more than outweighed by the advantages.
Hopefully this will help to clear this subject up. Check out the post I made in the other thread for more information.
Niffy
My deck certainly has raised a few eyebrows, normally accompanied by the question is that a record player? or more often what is that? Often followed by do you mind if I take a photo. Quite satisfying to have something I've worked so hard on being universally appreciated.
Jim.
As always, fantastic quality of workmanship. Your latest carriage version looks very solid and well thought out. I'm right along side you in you decision to lower the rail as close to the record surface as possible (my carriage has a similar clearance above the record surface). This will minimize any possible warp wow and help to reduce tracking force variation. You probably already know my opinions on keeping the arm length nice and short. Eliminate the armtube and you eliminate armtube resonance, simple.
On the earlier discussion about effective mass.
Bearing friction is proportional to arm mass via the coefficient of friction of the bearing as you have suggested. With an air bearing the coefficient of friction is SO low that friction is effectively zero in both the vertical and lateral planes. This does NOT mean that effective masses will effectively be the same. The effective mass describes how the arm will accelerate and move for a given input force/frequency. An arm with a higher mass will move less than one with a lower mass. A higher mass will control the cartridge better but will result in a lower cantilever resonance which may cause it's own problems. I discussed this in some depth in the diy linear tonearm thread about a year ago. In my opinion the ideal effective mass is dependent upon cartridge compliance, the lowest frequency cut into the record and the highest frequency of anything that could disturb replay eg warps. As these are completely different in the vertical and horizontal planes the ideal masses will be completely different. The ideal lateral effective mass is much higher than the ideal vertical.
However making the difference between the two masses too great can cause some issues.
If you imagine a signal that is cut in only one channel. The stylus in this case will move at 45°. If the effective masses are the same the cartridge body will move a small amount vertically and the same amount laterally, also at 45° eg it will move a small amount in the same direction as the stylus.
Now imagine the lateral mass is very high. The cartridge body will still move vertically by a small amount but not laterally. The cartridge body is only moving vertically which will cause an output in both channels. This will result in a small amount of crosstalk between channels reducing channel separation. The amount of this separation will decrease at about 6dB/octave.
Records are recorded in mono below about 120hz. As long as the ratio between the two masses is kept to about 1:4 then by the time you get to 120hz the crosstalk is down to about -30dB. About as good as any cartridge can pick up. Above this frequency the separation improves rapidly.
So is this actually a problem. NO. One of the main improvement of a linear tracking tonearm over a pivoted design is the improvement in stereo imaging. Any theoretical disadvantage to having different effective masses is more than outweighed by the advantages.
Hopefully this will help to clear this subject up. Check out the post I made in the other thread for more information.
Niffy
Great info. Thanks for sharing. Probably thats why NAD Flat tone arm didn't become popular.
Regards.
Regards.
Last edited:
Ratios
Hi Niffy,
My hat is off to your professional effort designing and building your tone arm.
Now my question: I understand the concept of ratios, but how do you tell which of the two numbers refers to the lateral mass and which to the vertical mass? Is there a convention?
Sincerely,
Ralf
Hi Niffy,
My hat is off to your professional effort designing and building your tone arm.
Now my question: I understand the concept of ratios, but how do you tell which of the two numbers refers to the lateral mass and which to the vertical mass? Is there a convention?
Sincerely,
Ralf
Hi Niffy,
Thank your for your inputs!
Actually, I don’t disagree with what you said regarding of effective mass. What I was trying to say is there is a difference in vertical and horizontal effective masses for air bearing arm. However, the difference is so small. It is not significant in playing back for air bearing arm, especially, for my kind of air bearing arm. You are talking about theoretical effective mass in which friction is not a part of equation. I was talking about effective mass in reality. Friction is a part of equation.
I do think the difference in vertical and horizontal masses may cause problem but I did see any clear explanations so far.
To further illustrate my view, let’s look the formula I used before.
Fv(The force required to move the arm vertically)=μWv
Fh(the force required to move the arm horizontally)=μWh
Where μ is coefficient of friction. Wh is horizontal effective mass. Wv is vertical effective mass.
For pivot arms,
Where μ, coefficient of friction, is same vertically and horizontally because it is on the same pivot. Wv is same as Wh. Its vertical and horizontal effective masses are same. So, the resonance frequency of cartridge and arm is same vertically and horizontally. Its underlying assumption is the arm movement is free of any resistance. In other words, there is no or very little friction. What you said is completely correct for pivot arms in reality.
For air bearing arms,
Where μ is same vertically and horizontally. Both vertical and horizontal coefficient of friction are same because they are both on same air film. But its vertical and horizontal effective masses are different. The interactions of cartridge compliance and effective mass are different vertically and horizontally. However, the difference is very small because both vertical and horizontal coefficients of friction is same, just as pivot arm’s. And the friction is almost equal to zero. In other words, the vertical and horizontal resonance frequencies are not same but very similar.
For mechanical linear arms,
Where μ, coefficient of friction, is NOT same vertically and horizontally. Its vertical coefficient of friction is SMALLER than horizontal coefficient of friction. Its vertical friction is smaller because its wheels act as a pivot only. But the same wheels have to carry the whole mass crossing record. Its horizontal friction is much higher than it vertical friction. Due to the difference in friction, the interactions of cartridge compliance and effective mass are different. So, the vertical and horizontal resonance frequencies are not same either. This difference is significant enough to cause problems.
Again, I don’t think your opinion is contradict to what I was saying.
Jim
Thank your for your inputs!
Actually, I don’t disagree with what you said regarding of effective mass. What I was trying to say is there is a difference in vertical and horizontal effective masses for air bearing arm. However, the difference is so small. It is not significant in playing back for air bearing arm, especially, for my kind of air bearing arm. You are talking about theoretical effective mass in which friction is not a part of equation. I was talking about effective mass in reality. Friction is a part of equation.
I do think the difference in vertical and horizontal masses may cause problem but I did see any clear explanations so far.
To further illustrate my view, let’s look the formula I used before.
Fv(The force required to move the arm vertically)=μWv
Fh(the force required to move the arm horizontally)=μWh
Where μ is coefficient of friction. Wh is horizontal effective mass. Wv is vertical effective mass.
For pivot arms,
Where μ, coefficient of friction, is same vertically and horizontally because it is on the same pivot. Wv is same as Wh. Its vertical and horizontal effective masses are same. So, the resonance frequency of cartridge and arm is same vertically and horizontally. Its underlying assumption is the arm movement is free of any resistance. In other words, there is no or very little friction. What you said is completely correct for pivot arms in reality.
For air bearing arms,
Where μ is same vertically and horizontally. Both vertical and horizontal coefficient of friction are same because they are both on same air film. But its vertical and horizontal effective masses are different. The interactions of cartridge compliance and effective mass are different vertically and horizontally. However, the difference is very small because both vertical and horizontal coefficients of friction is same, just as pivot arm’s. And the friction is almost equal to zero. In other words, the vertical and horizontal resonance frequencies are not same but very similar.
For mechanical linear arms,
Where μ, coefficient of friction, is NOT same vertically and horizontally. Its vertical coefficient of friction is SMALLER than horizontal coefficient of friction. Its vertical friction is smaller because its wheels act as a pivot only. But the same wheels have to carry the whole mass crossing record. Its horizontal friction is much higher than it vertical friction. Due to the difference in friction, the interactions of cartridge compliance and effective mass are different. So, the vertical and horizontal resonance frequencies are not same either. This difference is significant enough to cause problems.
Again, I don’t think your opinion is contradict to what I was saying.
Jim
In addition to eliminate arm tube resonance, short arm makes the cantilever more sensitive to movements of air bearing. This will put less stress on the cantilever.
Jim
The success of my latest head shell triggered me to do another similar head shell for my other air bearing arm. This time I made it even ticker. It is about 11 mm thick on the part which has direct contact with cartridge. The other one is about 8 mm thick. The new head shell is about 7 mm shorter than its previous one and made with all solid 2024 aluminum. The air bearing is now about 5 mm above the surface of record.
I also redid the counter weight part. It is much shorter and close to shaft now.
I thought I completely satisfied with previous head shell. New head shell further improves my air bearing arm with enhanced bass and sound staging.
I also redid the counter weight part. It is much shorter and close to shaft now.
I thought I completely satisfied with previous head shell. New head shell further improves my air bearing arm with enhanced bass and sound staging.
Last edited:
Some of you may remember that I did a moving shaft style air bearing arm, but I gave it up later on. Please look the early part of this thread. Here is a photo of my moving shaft air bearing arm.
The reason to give it up was I could hear the difference outer groove and inner groove. What to cause this could be inaccuracy of its shaft. I used a stock linear movement shaft, which was not for air bearing. At inner groove, the shaft was at its longest position. The shaft might have slightly movements which caused distortions. Although I believe that moving shaft arm can be further improved, in my opinion, it may not be able to outperform 1” moving air bearing arms I am using now. I can’t hear any difference between inner groove and outer groove on my two 1” moving air bearing arms. The dynamics is explosive and bass is beyond what I expected for an analogue tone arm on my 1" moving bearing arms. However, since I have two 1/2” air bearings in hand without any other uses. I may try to make a different style of moving shaft arm if one day I feel the desire to do another air bearing arm. I will order an aluminum shaft which is merely for air bearing. The precision of the shaft is crucial for high performance of air bearing arms.
Here is the plan I have in my mind. I posted it here to solicit opinions and suggestions before I will actually work on the new moving shaft arm.
The basic idea underlying the design is to try to make the stylus close to center line of air bearing shaft as much as I can. I am always wondering what happens if the line of stylus moving overlaps the pivot line of shaft. Obviously, it is impossible to do it in reality due to wrap of records. It also makes adjusting VTF very complicated. To my experience, the shorter arm not only eliminates arm tube resonance but also makes air bearing more sensitive to stylus movements.
I will make the distance 25 mm from stylus to the center of shaft. On the right side, it is eddy current damping device. Two magnets form a magnetic field. The shaft will be aluminum. It moves in between two magnets. The gap of magnets is adjustable so I can control the strength of damping force.
For this new moving shaft arm, I understand that the difference between vertical and horizontal masses will be even bigger. I am thinking of doing a test to measure vertical and lateral resonance frequencies as John Elison at Audio Asylum did.
Vinyl Asylum: I have discovered what I believe to be a more accurate method of measuring arm/cartridge resonance.... by John Elison
If lateral and vertical resonance frequencies are similar or even same which I don’t expect to be same, I can conclude that the difference in lateral effective mass and vertical effective mass is not important. For now, at least to my ear, such difference doesn’t have too much impact.
The reason to give it up was I could hear the difference outer groove and inner groove. What to cause this could be inaccuracy of its shaft. I used a stock linear movement shaft, which was not for air bearing. At inner groove, the shaft was at its longest position. The shaft might have slightly movements which caused distortions. Although I believe that moving shaft arm can be further improved, in my opinion, it may not be able to outperform 1” moving air bearing arms I am using now. I can’t hear any difference between inner groove and outer groove on my two 1” moving air bearing arms. The dynamics is explosive and bass is beyond what I expected for an analogue tone arm on my 1" moving bearing arms. However, since I have two 1/2” air bearings in hand without any other uses. I may try to make a different style of moving shaft arm if one day I feel the desire to do another air bearing arm. I will order an aluminum shaft which is merely for air bearing. The precision of the shaft is crucial for high performance of air bearing arms.
Here is the plan I have in my mind. I posted it here to solicit opinions and suggestions before I will actually work on the new moving shaft arm.
The basic idea underlying the design is to try to make the stylus close to center line of air bearing shaft as much as I can. I am always wondering what happens if the line of stylus moving overlaps the pivot line of shaft. Obviously, it is impossible to do it in reality due to wrap of records. It also makes adjusting VTF very complicated. To my experience, the shorter arm not only eliminates arm tube resonance but also makes air bearing more sensitive to stylus movements.
I will make the distance 25 mm from stylus to the center of shaft. On the right side, it is eddy current damping device. Two magnets form a magnetic field. The shaft will be aluminum. It moves in between two magnets. The gap of magnets is adjustable so I can control the strength of damping force.
For this new moving shaft arm, I understand that the difference between vertical and horizontal masses will be even bigger. I am thinking of doing a test to measure vertical and lateral resonance frequencies as John Elison at Audio Asylum did.
Vinyl Asylum: I have discovered what I believe to be a more accurate method of measuring arm/cartridge resonance.... by John Elison
If lateral and vertical resonance frequencies are similar or even same which I don’t expect to be same, I can conclude that the difference in lateral effective mass and vertical effective mass is not important. For now, at least to my ear, such difference doesn’t have too much impact.
Last edited:
Hi Jim
I like the idea of a moving shaft supported by two air bearings. I would use 2024 aluminum tubing and have it centerless ground and hard anodized. I would damp the inside with some lightweight material such as wool etc.
I don't think the eddy current idea will work. All the eddy current devices I have seen, required that either the magnet or the aluminum part has to spin relatively quickly to generate the necessary current. the relative motion between the air bearing shaft and the magnets in your design is almost non-existent because of the slow motion of the shaft. This is just my opinion.
Sincerely,
Ralf
I like the idea of a moving shaft supported by two air bearings. I would use 2024 aluminum tubing and have it centerless ground and hard anodized. I would damp the inside with some lightweight material such as wool etc.
I don't think the eddy current idea will work. All the eddy current devices I have seen, required that either the magnet or the aluminum part has to spin relatively quickly to generate the necessary current. the relative motion between the air bearing shaft and the magnets in your design is almost non-existent because of the slow motion of the shaft. This is just my opinion.
Sincerely,
Ralf
The sectioned air bearings would require a longer shaft and more horizontal mass but maybe more important is a thermally stable way of mounting the bearings so as to not affect the tight tolerances required.
Excellent stability is obvious and maybe different air pressure in each so as to spread any kind of peak contribution or pulse from forming
Regards
David
Excellent stability is obvious and maybe different air pressure in each so as to spread any kind of peak contribution or pulse from forming
Regards
David
Hi Ralf
It can keep the shaft to move consistently to arrange the air bearings on two sides in stead of putting air bearings on one side.
The aluminum shaft I was talking about is stock shaft from Oav. It is 6061 coated with ceramic. I would like to have a hollow shaft, but to ask them to drill a hole all way through the shaft will cost me $500. It's too much for me. If I use a solid shaft, it should be ok as long as it is not too heavy. A 1/2" 17" long aluminum shaft is about 150 grams. It is ok if shaft plus head shell, counter weight and cartridge is around 200 gram.
The drag force of Eddy Current device depends on magnetic field, the velocity of the motion, the effective resistance of the plate and the size of the magnetic patch.
https://physics.stackexchange.com/q...-eddy-currents-of-a-conductor-is-this-correct
I will use the largest magnets and the strongest magnets possible. I believe it will generate some drag force. Does it have enough force? I can’t tell. It seems to me that it is too complicated for me to compute its force. The beauty of Eddy Current is its force changes with the speed of shaft. Once the shaft moves fast due to eccentricity, it will generate stranger force.
Thank you for your inputs!
Jim
It can keep the shaft to move consistently to arrange the air bearings on two sides in stead of putting air bearings on one side.
The aluminum shaft I was talking about is stock shaft from Oav. It is 6061 coated with ceramic. I would like to have a hollow shaft, but to ask them to drill a hole all way through the shaft will cost me $500. It's too much for me. If I use a solid shaft, it should be ok as long as it is not too heavy. A 1/2" 17" long aluminum shaft is about 150 grams. It is ok if shaft plus head shell, counter weight and cartridge is around 200 gram.
The drag force of Eddy Current device depends on magnetic field, the velocity of the motion, the effective resistance of the plate and the size of the magnetic patch.
https://physics.stackexchange.com/q...-eddy-currents-of-a-conductor-is-this-correct
I will use the largest magnets and the strongest magnets possible. I believe it will generate some drag force. Does it have enough force? I can’t tell. It seems to me that it is too complicated for me to compute its force. The beauty of Eddy Current is its force changes with the speed of shaft. Once the shaft moves fast due to eccentricity, it will generate stranger force.
Thank you for your inputs!
Jim
Hi David,
It is very critical how to mount the air bearing. I plan to mount one air bearing on one side fixed. The air bearing on another side is adjustable and to adjust the center of one air bearing while feeding both air bearings with normal compressed air in order to get the perfect line up.
Jim
It is very critical how to mount the air bearing. I plan to mount one air bearing on one side fixed. The air bearing on another side is adjustable and to adjust the center of one air bearing while feeding both air bearings with normal compressed air in order to get the perfect line up.
Jim
Hi Jim,
I've been in the hell of moving house and haven't had the opportunity to reply to any of the recent posts.
The moving shaft concept should offer the lowest possible friction as the air hose doesn't move. It may however have a higher mass which may or may not be advantageous, this will probably depend on cartridge compliance.
Reducing the effective length of the arm to being so short can have definite advantages in resonance control. It will also create less torque reaction about the bearings which should theoretically make the arm move more smoothly. Any improvement in this area is likely to be very small as the bearing friction is so low in the first place.
Making the arm so short can have disadvantages as well. Different thicknesses of record will have significant VTA variation. Even though you have an excellent warp flattening clamping system it cannot eliminate all warps. Having the vertical pivot mounted high above the record combined with an ultra short arm may cause audible warp wow. I notice in your diagram that the shaft is broken at the headshell to allow the cartridge to sit within it and to allow the rail to be as low as possible. I think that this is essential.
I think magnetic damping is a really good idea. Very little damping is likely to be necessary unless the arm is excessively heavy. Silicone fluid is messy and is good for higher levels of damping. In this design magnetic damping is probably the best approach. The configuration you have shown would have greater damping laterally than vertically which,as the lateral mass is greater, is probably what you want.
I'll be very interested to see what you come up with if you pursue this idea.
Niffy
I've been in the hell of moving house and haven't had the opportunity to reply to any of the recent posts.
The moving shaft concept should offer the lowest possible friction as the air hose doesn't move. It may however have a higher mass which may or may not be advantageous, this will probably depend on cartridge compliance.
Reducing the effective length of the arm to being so short can have definite advantages in resonance control. It will also create less torque reaction about the bearings which should theoretically make the arm move more smoothly. Any improvement in this area is likely to be very small as the bearing friction is so low in the first place.
Making the arm so short can have disadvantages as well. Different thicknesses of record will have significant VTA variation. Even though you have an excellent warp flattening clamping system it cannot eliminate all warps. Having the vertical pivot mounted high above the record combined with an ultra short arm may cause audible warp wow. I notice in your diagram that the shaft is broken at the headshell to allow the cartridge to sit within it and to allow the rail to be as low as possible. I think that this is essential.
I think magnetic damping is a really good idea. Very little damping is likely to be necessary unless the arm is excessively heavy. Silicone fluid is messy and is good for higher levels of damping. In this design magnetic damping is probably the best approach. The configuration you have shown would have greater damping laterally than vertically which,as the lateral mass is greater, is probably what you want.
I'll be very interested to see what you come up with if you pursue this idea.
Niffy
Hi Niffy,
Although the moving shaft air bearing arm doesn’t have the possible resistance from air tubing, I feel moving bearing construction produces better sound. However, it is not conclusive. On my moving air bearing arms, air tubings are not problem at all. I think moving air bearing arm has consistent parameters from outer groove to inner groove. So, its performance is consistent. For moving shaft arm as my old one, which has both air bearings on one side, its parameters may change from outer groove to inner groove. This why I could heard the difference of outer groove and inner groove. For Walker Audio black diamond V arm, its shaft is at its optimum position while the cartridge tracks inner groove, which is difficult to track. When its shaft is not at its optimum position, the cartridge tracks outer groove, which is easier to track. The movements of my old moving shaft arm is the opposite of black diamond V.
I think short arm does reduce arm tube resonance. Another advantage of short arm is it reduces moments of inertia. I further reduced the counter weight part. It is same as arm tube. Short counter weight reduces resonance and inertia.
I have read Stereophile review of Versa Dynamics 2.0 recently. I found that my arm is becoming very similar to Versa arm. Versa head shell is magnesium. Mine is combination of magnesium and 2024 aluminum alloy. 2024 aluminum alloy has 1.5% magnesium. My head shell attaches upper 1/3 of air bearing. Versa is on the upper 1/2 of air bearing. Versa has very short arm. Mine has the shortest arm I can make. The interesting part is Versa used eddy current damping device, too. But they abandoned the eddy current device in their later version of arm. I am not sure why, but they might think that short arm and counter weight have very little or no inertia. Therefore, damping is not necessary. The difference is I use 1” air bearing. They used 3/4” air bearing. My air tube is latex. Their air tubing seems like PVC tubing. I think both of 1” air bearing and latex tubing are better than theirs.
Versa Dynamics 2.0 LP player | Stereophile.com
Jim
Although the moving shaft air bearing arm doesn’t have the possible resistance from air tubing, I feel moving bearing construction produces better sound. However, it is not conclusive. On my moving air bearing arms, air tubings are not problem at all. I think moving air bearing arm has consistent parameters from outer groove to inner groove. So, its performance is consistent. For moving shaft arm as my old one, which has both air bearings on one side, its parameters may change from outer groove to inner groove. This why I could heard the difference of outer groove and inner groove. For Walker Audio black diamond V arm, its shaft is at its optimum position while the cartridge tracks inner groove, which is difficult to track. When its shaft is not at its optimum position, the cartridge tracks outer groove, which is easier to track. The movements of my old moving shaft arm is the opposite of black diamond V.
I think short arm does reduce arm tube resonance. Another advantage of short arm is it reduces moments of inertia. I further reduced the counter weight part. It is same as arm tube. Short counter weight reduces resonance and inertia.
I have read Stereophile review of Versa Dynamics 2.0 recently. I found that my arm is becoming very similar to Versa arm. Versa head shell is magnesium. Mine is combination of magnesium and 2024 aluminum alloy. 2024 aluminum alloy has 1.5% magnesium. My head shell attaches upper 1/3 of air bearing. Versa is on the upper 1/2 of air bearing. Versa has very short arm. Mine has the shortest arm I can make. The interesting part is Versa used eddy current damping device, too. But they abandoned the eddy current device in their later version of arm. I am not sure why, but they might think that short arm and counter weight have very little or no inertia. Therefore, damping is not necessary. The difference is I use 1” air bearing. They used 3/4” air bearing. My air tube is latex. Their air tubing seems like PVC tubing. I think both of 1” air bearing and latex tubing are better than theirs.
Versa Dynamics 2.0 LP player | Stereophile.com
Jim
Have you noticed any deflection of the needle at each extreme ends of an LP because of the air tubing having to twist along its path?
A servo at the base of the air tube to track the arm would solve this area of concern but adds another level of complexity...alas
How are you dealing with VTA changes and keeping for and aft dimensions the same?
Regards
David
A servo at the base of the air tube to track the arm would solve this area of concern but adds another level of complexity...alas
How are you dealing with VTA changes and keeping for and aft dimensions the same?
Regards
David
Hi David,
There is no deflection of the stylus at both extreme ends of an LP because air bearing can have much higher load than the load from a twisted air tubing. So, the position of air bearing relating to the shaft will not change. Therefore, the stylus will be deflected at extreme ends of an LP due to twisted air tubing. A twisted air tubing may add a little resistance( friction) to air bearing horizontally and vertically.
I thought to use a micro stepper motor to move the base of air tubing according to air bearing location. But I gave it up. The reasons for that was it adds complexity of construction. Motor may introduce noise as well. In addition to that, air tubing introduces resistance both horizontally and vertically. A stepper motor only eliminates horizontal resistance. So, it is not that effective.
I am using latex air tubing and air pressure can be pumped up to 58 psi which is good enough for this kind of air bearing. Latex tubing is much more flexible than PVC. I don’t think it has any negative impact on the sound.
I have a 7 lbs outer ring so warp is not a problem to me. VTA won’t change too much due to minimization of warp. My outer ring may well be the next best thing after vacuum system.
Jim
There is no deflection of the stylus at both extreme ends of an LP because air bearing can have much higher load than the load from a twisted air tubing. So, the position of air bearing relating to the shaft will not change. Therefore, the stylus will be deflected at extreme ends of an LP due to twisted air tubing. A twisted air tubing may add a little resistance( friction) to air bearing horizontally and vertically.
I thought to use a micro stepper motor to move the base of air tubing according to air bearing location. But I gave it up. The reasons for that was it adds complexity of construction. Motor may introduce noise as well. In addition to that, air tubing introduces resistance both horizontally and vertically. A stepper motor only eliminates horizontal resistance. So, it is not that effective.
I am using latex air tubing and air pressure can be pumped up to 58 psi which is good enough for this kind of air bearing. Latex tubing is much more flexible than PVC. I don’t think it has any negative impact on the sound.
I have a 7 lbs outer ring so warp is not a problem to me. VTA won’t change too much due to minimization of warp. My outer ring may well be the next best thing after vacuum system.
Jim
Every cartridge has a VTA sweet spot and requires certain horizontal orientations that must be met, meaning you must raise or lower the 1" shaft or beam.
If your diamond to air pivot point center is say 2.5" that would mean the tonearm mounting base of the stationery beam would have to ark around this 5" circle to maintain the same spot without changing the for and aft point of the linear track line of the record.
This is what I was asking regardless of a perfectly flat record, which is mandarory on a short arm.
Or are you just readjusting the cartridge when you find the optimum VTA?
That would be a hassle of course..,
Regards
David
If your diamond to air pivot point center is say 2.5" that would mean the tonearm mounting base of the stationery beam would have to ark around this 5" circle to maintain the same spot without changing the for and aft point of the linear track line of the record.
This is what I was asking regardless of a perfectly flat record, which is mandarory on a short arm.
Or are you just readjusting the cartridge when you find the optimum VTA?
That would be a hassle of course..,
Regards
David