Hi David,
I have two ways to adjust VTA. Please see the photo.
A. I can do some rough adjustment on the head shell. The main propose of rough adjustment is to let the air bearing close to the surface of record as much as I can for different cartridge. It is now about 3 mm. In the meantimes, I keep VTA approximately correct, say 20 degree.
B. I can do very fine adjustments of VTA on the micrometer head. I can also adjust VTA while playing record to find the sweet spot of VTA. The movements can be very fine. Fine adjustments of VTA on my other air bearing arm is not as easy as this one. I can't adjust VTA while playing record on another arm.
I hope I answered your question.
Jim
I have two ways to adjust VTA. Please see the photo.
A. I can do some rough adjustment on the head shell. The main propose of rough adjustment is to let the air bearing close to the surface of record as much as I can for different cartridge. It is now about 3 mm. In the meantimes, I keep VTA approximately correct, say 20 degree.
B. I can do very fine adjustments of VTA on the micrometer head. I can also adjust VTA while playing record to find the sweet spot of VTA. The movements can be very fine. Fine adjustments of VTA on my other air bearing arm is not as easy as this one. I can't adjust VTA while playing record on another arm.
I hope I answered your question.
Jim
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Ok
If A is slotted and can be moved up and down then you will maintain the same position since it stays inside the 'circle' pivot envelope
B however will pull the diamond away from the linear track line if abused. It is outside the 'circle' and the higher you go with that one, the diamond will wind up behind the tracking line eventually.
Nice to have both adjustments available
Regards
David
If A is slotted and can be moved up and down then you will maintain the same position since it stays inside the 'circle' pivot envelope
B however will pull the diamond away from the linear track line if abused. It is outside the 'circle' and the higher you go with that one, the diamond will wind up behind the tracking line eventually.
Nice to have both adjustments available
Regards
David
Hi David,
Yes. You are right. If I raise or low VTA by using micrometer head, every 2 mm will cause the stylus off the perpendicular line about + or - 1 mm. So, if I adjust VTA under 1 mm, I usually don’t check alignment. But if I adjust VTA more than 1 mm, I usually check alignment again. However, it is very easy and quick to realign the cartridge on my air bearing arm.
Jim
Yes. You are right. If I raise or low VTA by using micrometer head, every 2 mm will cause the stylus off the perpendicular line about + or - 1 mm. So, if I adjust VTA under 1 mm, I usually don’t check alignment. But if I adjust VTA more than 1 mm, I usually check alignment again. However, it is very easy and quick to realign the cartridge on my air bearing arm.
Jim
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Recently, I did some arm/cart resonance frequency tests for my diy air bearing arm. In my previous posts, I stated that although there is significant difference in lateral effective mass and vertical effective mass, lateral and vertical resonance frequencies can be very similar for air bearing arms. But it was only a guess and I had no evidence to support such statement.
People always criticize line tracking arm because its lateral and vertical effective masses are different. The difference in masses will cause the difference in resonance frequencies. Therefore, it is not desirable for tone arms.
However, my tests show that for my air bearing arm, lateral and vertical resonance frequencies are very close.
The method I used to test resonance frequencies was posted by John Elison at Audio Asylum.Thanks John!
Vinyl Asylum: I have discovered what I believe to be a more accurate method of measuring arm/cartridge resonance.... by John Elison
He used Sony Sound Forge software and I used Adobe Audition. Here are the results.
The results surprised to me a bit. It seems to me that it is too good for my air bearing arm. Both vertical and lateral resonance frequencies are very close. The software I used was Adobe Audition. In Audition, if I move the cursor( vertical red line) over the green or blue wave forms, I can get overall frequency at this point. So, I got
Lateral resonance frequency: 3.97 Hz(left), 3.84 Hz(right)
Vertical resonance frequency: 4.37 Hz(left), 4.37 Hz(right)
I always thought that lateral effective mass of an air bearing arm is much heavier than its vertical effective mass. The test results tell me different story. If the test method is correct, the results indicate that both lateral effective mass and vertical effective mass are very close for my air bearing arm, especially, for short arms. Therefore, any criticism about difference in lateral mass and vertical mass is unfounded for my kind of air bearing arm.
Due to both lateral and vertical resonance frequencies are within 2-7 Hz, which is warp resonance frequencies, a device to reduce warps is needed. I am using a heavy 6 lbs outer ring to reduce warps. To use a heavy outer ring may have negative impact on the stability of the turntable. So, it is a compromise between reducing warp resonance and stabilizing turntable speed. A vacuum suction platter should be a perfect solution.
People always criticize line tracking arm because its lateral and vertical effective masses are different. The difference in masses will cause the difference in resonance frequencies. Therefore, it is not desirable for tone arms.
However, my tests show that for my air bearing arm, lateral and vertical resonance frequencies are very close.
The method I used to test resonance frequencies was posted by John Elison at Audio Asylum.Thanks John!
Vinyl Asylum: I have discovered what I believe to be a more accurate method of measuring arm/cartridge resonance.... by John Elison
He used Sony Sound Forge software and I used Adobe Audition. Here are the results.
The results surprised to me a bit. It seems to me that it is too good for my air bearing arm. Both vertical and lateral resonance frequencies are very close. The software I used was Adobe Audition. In Audition, if I move the cursor( vertical red line) over the green or blue wave forms, I can get overall frequency at this point. So, I got
Lateral resonance frequency: 3.97 Hz(left), 3.84 Hz(right)
Vertical resonance frequency: 4.37 Hz(left), 4.37 Hz(right)
I always thought that lateral effective mass of an air bearing arm is much heavier than its vertical effective mass. The test results tell me different story. If the test method is correct, the results indicate that both lateral effective mass and vertical effective mass are very close for my air bearing arm, especially, for short arms. Therefore, any criticism about difference in lateral mass and vertical mass is unfounded for my kind of air bearing arm.
Due to both lateral and vertical resonance frequencies are within 2-7 Hz, which is warp resonance frequencies, a device to reduce warps is needed. I am using a heavy 6 lbs outer ring to reduce warps. To use a heavy outer ring may have negative impact on the stability of the turntable. So, it is a compromise between reducing warp resonance and stabilizing turntable speed. A vacuum suction platter should be a perfect solution.
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Here is another update for my diy air bearing arms.
I was using latex tubing for air supply of air bearing arm. The shortcoming of latex tubing is it has very low working pressure, about 30 psi. I kept the pressure at 55 psi. When the temperature gets higher, its working pressure gets even lower. One of my air bearing arm bursted its air supply tubing during a hot summer day, so I started to look for an alternative. Finally I find a perfect air supply tubing for air bearing arm. It is Tygon E-3603 1/32” ID 3/32” OD tubing. That tubing has almost same feel as latex’s. Its durometer hardness is 56 which is higher than latex. Latex has about 30. But its maximum working pressure is 69 psi which is way higher than latex tubing’s. The Tygon tubing has 1/32” ID and 3/32 OD, which is half size of the latex tubing I used. So, it is even more flexible than 1/16” ID latex tubing. The best part of Tygon tubing is its maximum pressure rating is 69 psi. The higher air pressure, the stiffer the air bearing is. Kzuma airline arm uses 65 psi. I tried 70 psi. Love it! I don’t think I can find a better air supply tubing than Tygon E-3603. It is the ultimate air supply tubing for air bearing arm!
I was using latex tubing for air supply of air bearing arm. The shortcoming of latex tubing is it has very low working pressure, about 30 psi. I kept the pressure at 55 psi. When the temperature gets higher, its working pressure gets even lower. One of my air bearing arm bursted its air supply tubing during a hot summer day, so I started to look for an alternative. Finally I find a perfect air supply tubing for air bearing arm. It is Tygon E-3603 1/32” ID 3/32” OD tubing. That tubing has almost same feel as latex’s. Its durometer hardness is 56 which is higher than latex. Latex has about 30. But its maximum working pressure is 69 psi which is way higher than latex tubing’s. The Tygon tubing has 1/32” ID and 3/32 OD, which is half size of the latex tubing I used. So, it is even more flexible than 1/16” ID latex tubing. The best part of Tygon tubing is its maximum pressure rating is 69 psi. The higher air pressure, the stiffer the air bearing is. Kzuma airline arm uses 65 psi. I tried 70 psi. Love it! I don’t think I can find a better air supply tubing than Tygon E-3603. It is the ultimate air supply tubing for air bearing arm!
I just realized that Photobucket doesn’t host third party public images without upgrading my account now. Most of images don’t show in my post. If you really want to see the photos, please right click to open image in new tab or new window. You will be redirected to Photobucket site to see the original image.
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Hi Jim.
Great to see you still pushing your arm design forwards.
The new tygon tubing sounds like a great find. Being able to double the air pressure should make the bearing incredibly stiff. If some of my theories about air bearings are correct this should allow you to slightly reduce the amount of damping required for optimal performance.
The resonant frequency test results are also very interesting. With most linear tracking arms the vertical and lateral effective masses are quite different resulting in different resonant frequencies (they are in my arm). Contrary to popular belief this is not necessarily problematic. Effective mass isn't just about mass but about how that mass is distributed. I could easily design a linear arm with 50g lateral mass and 100g vertical effective mass. I could but I won't as it would be pointless.
It is very odd that John Elison managed to get different results for left and right channels. At resonance you are actually measuring the cartridge body movement and that HAS to be the same frequency for both channels. Did you measure both channels at the same time or on separate runs? Very odd indeed.
Your arm would appear to have a vertical effective mass of about 90g. This would normally be considered way to high with the resonant frequency of 4.37hz. Right in the middle of the warp frequency range, as you pointed out.
However I think that your approach is inspired. Rather than making the arm deal with warps and all of their associated problems, GET RID OF THE WARPS.
No warps means no warp wow, no warp induced tracking force variation and no VTA or azimuth variations. (no current arm design can do anything about the last two)
Also effective mass doesn't have to be kept in a range where resonance is above the frequency of warps as there are no warps.
The main mechanism for controlling the motion of the cartridge (below the arms bending mode resonance) is mass. More mass means the cartridge body moves less relative to the stylus's movement, a good thing. With your 4.37hz resonance the cartridge body will move a lot less than with the normally recommended 10hz resonance, about 6dB less.
When I initially started my design work I built a measurement rig and measured the actual level of warps in a random sample of my record collection. These measurements seem to suggest that some records have a slight wrinkling that no clamping system would be able to smooth out. This wrinkling seems to be at about 5-6hz (from memory, I don't have the measurements on me). These may cause a problem as they are close to the resonant frequency of your arm. They were, however, of a very low amplitude so should be easily controlled with only light damping and are unlikely to cause anything audible.
With many ultra-high end decks having vacuum hold down systems or peripheral clamps it surprises me that high effective mass arms are not common. They would have to be used only with the decks for which they were designed. I think that the reason that we don't see them is reviewer bias. Designing a record player as a single unit has many advantages but the reviewer would want to try it with his/her favourite arm. Reviewers don't like decks where they have no choice in the arm they use.
I have found that increased effective mass leads to a sound that is more solid and cleaner.
Niffy
Great to see you still pushing your arm design forwards.
The new tygon tubing sounds like a great find. Being able to double the air pressure should make the bearing incredibly stiff. If some of my theories about air bearings are correct this should allow you to slightly reduce the amount of damping required for optimal performance.
The resonant frequency test results are also very interesting. With most linear tracking arms the vertical and lateral effective masses are quite different resulting in different resonant frequencies (they are in my arm). Contrary to popular belief this is not necessarily problematic. Effective mass isn't just about mass but about how that mass is distributed. I could easily design a linear arm with 50g lateral mass and 100g vertical effective mass. I could but I won't as it would be pointless.
It is very odd that John Elison managed to get different results for left and right channels. At resonance you are actually measuring the cartridge body movement and that HAS to be the same frequency for both channels. Did you measure both channels at the same time or on separate runs? Very odd indeed.
Your arm would appear to have a vertical effective mass of about 90g. This would normally be considered way to high with the resonant frequency of 4.37hz. Right in the middle of the warp frequency range, as you pointed out.
However I think that your approach is inspired. Rather than making the arm deal with warps and all of their associated problems, GET RID OF THE WARPS.
No warps means no warp wow, no warp induced tracking force variation and no VTA or azimuth variations. (no current arm design can do anything about the last two)
Also effective mass doesn't have to be kept in a range where resonance is above the frequency of warps as there are no warps.
The main mechanism for controlling the motion of the cartridge (below the arms bending mode resonance) is mass. More mass means the cartridge body moves less relative to the stylus's movement, a good thing. With your 4.37hz resonance the cartridge body will move a lot less than with the normally recommended 10hz resonance, about 6dB less.
When I initially started my design work I built a measurement rig and measured the actual level of warps in a random sample of my record collection. These measurements seem to suggest that some records have a slight wrinkling that no clamping system would be able to smooth out. This wrinkling seems to be at about 5-6hz (from memory, I don't have the measurements on me). These may cause a problem as they are close to the resonant frequency of your arm. They were, however, of a very low amplitude so should be easily controlled with only light damping and are unlikely to cause anything audible.
With many ultra-high end decks having vacuum hold down systems or peripheral clamps it surprises me that high effective mass arms are not common. They would have to be used only with the decks for which they were designed. I think that the reason that we don't see them is reviewer bias. Designing a record player as a single unit has many advantages but the reviewer would want to try it with his/her favourite arm. Reviewers don't like decks where they have no choice in the arm they use.
I have found that increased effective mass leads to a sound that is more solid and cleaner.
Niffy
Hi Niffy,
Yes. The Tygon tubing is indeed nice one. Actually, I don’t use any damping device now. At the beginning, I worried about the ID of tubing might be too small. I did some basic calculation to make sure it has enough flow. In reality, it works like a champ. I modified the tubing a little bit because it is too soft to hold itself up.
I can’t see why the difference in lateral mass and vertical mass should be a problem either. Their resonance frequencies are more important. My tests show that lateral and vertical resonance frequencies can be very similar even their masses are significantly different for air bearing arm.
For the resonance frequency test, I got some difference, about 2 Hz in some areas, as well. I don’t know why. The track has two channel information. John manually measured the frequencies. I used the software’s measurements. I used Audition and he use Sound Forge.
Yes. I do think heavy arm produces better bass and more dynamic sound. My air bearing started with about 100 g. It is about 200 g now.
The outer ring not only can reduce warps but also it can help in other areas. Outer ring makes cartridge tracks better, too.
Jim
Yes. The Tygon tubing is indeed nice one. Actually, I don’t use any damping device now. At the beginning, I worried about the ID of tubing might be too small. I did some basic calculation to make sure it has enough flow. In reality, it works like a champ. I modified the tubing a little bit because it is too soft to hold itself up.
I can’t see why the difference in lateral mass and vertical mass should be a problem either. Their resonance frequencies are more important. My tests show that lateral and vertical resonance frequencies can be very similar even their masses are significantly different for air bearing arm.
For the resonance frequency test, I got some difference, about 2 Hz in some areas, as well. I don’t know why. The track has two channel information. John manually measured the frequencies. I used the software’s measurements. I used Audition and he use Sound Forge.
Yes. I do think heavy arm produces better bass and more dynamic sound. My air bearing started with about 100 g. It is about 200 g now.
The outer ring not only can reduce warps but also it can help in other areas. Outer ring makes cartridge tracks better, too.
Jim
It is said that heavy arm needs low compliance and lighter arms vice versa. Do air bearing arms which are totally friction less can get away with little compromise on compliance criteria ? or in other words suppose high compliance cartridge is used in heavy pivoted arm the mass/inertia comes in to play. Where as with air bearing one can get away using heavy tonearm. Right ?
regards.
regards.
Air bearing arms and other linear tracking arms perform the best using low or medium compliance cartridge, say, at least 15x 10-6 cm/dyn and under. The same compliance criteria for pivot arm is still true for air bearing or linear tracking arms. That is to keep the arm/cartridge resonance frequency under 20 Hz or even lower(lowest audible frequency) and above 7 Hz (highest warp resonance). Due to high friction ofmechnical linear arms, choosing a low compliance cartridge is very critical. I would recommend 12x10-6 cm/dyn and under.
Hmmm, does that method actually work? I might expect, as stylus-groove speed progressively slows, at some point the stylus-groove friction interface to change esp as to stick-slip. This would be a stimulus for headshell motion, even in a linear arm, not least due to VTA. And I might expect that effect to mimic what one is looking for........ that might explain your results, if normal cart-arm resonance(s) were also quite surpressed and stable? Your surprise might well be justified!
A quick look at the 3150Hz files you posted recently on another thread perhaps suggests about 5Hz and 12Hz, perhaps ?
HTH!
LD
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Hi LD,
Yes. The results were not what I expected. If the vertical resonance frequency is correct, it means that the vertical effective mass is about 100 grams. It seems too heavy to me. However, to further investigate the effectiveness of the method John discovered is beyond my knowledge and ability.
I plan to run another test by using Shure test LP. In that LP, I remember there is a resonance test track. But I can’t test vertical and lateral resonance separately.
Your estimate seems reasonable to me.
Jim
Yes. The results were not what I expected. If the vertical resonance frequency is correct, it means that the vertical effective mass is about 100 grams. It seems too heavy to me. However, to further investigate the effectiveness of the method John discovered is beyond my knowledge and ability.
I plan to run another test by using Shure test LP. In that LP, I remember there is a resonance test track. But I can’t test vertical and lateral resonance separately.
Your estimate seems reasonable to me.
Jim
The effects of bearing friction and effective mass are mainly unrelated. Jim can get away with a higher than normal effective mass not because of low bearing friction but because he has an excellent record clamping system that almost completely eradicates warps and with them all the problems they present.
With a mechanical linear tracking tonearm there are a couple of links between effective mass and bearing friction. The total carriage mass (which is the lateral effective mass) is directly related to bearing friction by the coefficient of friction of the bearing. Lower is on the whole better. The friction in the bearing will act to damp the motion of the arm to some extent. This level of damping will be fixed so you can't fine tune the arm by adjusting it.
Hi Jim
If your total carriage mass, including cartridge, is 200g and you have a measured lateral resonance of 3.9hz the lateral compliance would be 8.3um/mN. If I assume that the vertical compliance is also 8.3um/mN (vertical and lateral compliance are actually slightly different in most cartridges) then the vertical effective mass for a 4.37hz resonance would be 160g. This is a lot higher than my 90g estimate as I guessed your cartridge compliance at 15um/mN. What is the manufacturer stated compliance for your cartridge?
One of the problems with compliance specifications is that there isn't an industry standard. Most are dynamic measured at a frequency of 100 or 315hz some are lower frequency or even static. In most cartridges the compliance increases with lowering frequency, but not always. A rated compliance of 15um/mN at 100hz might be more like 20um/mN at 10hz. This doesn't make cartridge matching any easier.
I don't think that the resonant test results would be due to stick slide as the velocity of the stylus in the groove would still be very high when looked at on the scale of the stylus/groove. Could you point me in the direction of the thread LD mentioned, it may give some extra insight.
The method does seem reasonable. It's effectiveness would be maximised if the bearing is of a low friction design and the platter heavy as the rate of slowing would be slow and the resonant peek more accurately determined.
Normally I would agree that mechanical linear tracking arms are better suited to low compliance cartridges. I am, however, getting superb results using a highish compliance cartridge, 22um/mN in my mechanical linear arm. Having said that I am using bearings with level of friction closer to that of an air bearing than that of any ball race bearing. It would be interesting to hear how my arm sounds with a medium compliance cartridge.
With a mechanical linear tracking tonearm there are a couple of links between effective mass and bearing friction. The total carriage mass (which is the lateral effective mass) is directly related to bearing friction by the coefficient of friction of the bearing. Lower is on the whole better. The friction in the bearing will act to damp the motion of the arm to some extent. This level of damping will be fixed so you can't fine tune the arm by adjusting it.
Hi Jim
If your total carriage mass, including cartridge, is 200g and you have a measured lateral resonance of 3.9hz the lateral compliance would be 8.3um/mN. If I assume that the vertical compliance is also 8.3um/mN (vertical and lateral compliance are actually slightly different in most cartridges) then the vertical effective mass for a 4.37hz resonance would be 160g. This is a lot higher than my 90g estimate as I guessed your cartridge compliance at 15um/mN. What is the manufacturer stated compliance for your cartridge?
One of the problems with compliance specifications is that there isn't an industry standard. Most are dynamic measured at a frequency of 100 or 315hz some are lower frequency or even static. In most cartridges the compliance increases with lowering frequency, but not always. A rated compliance of 15um/mN at 100hz might be more like 20um/mN at 10hz. This doesn't make cartridge matching any easier.
I don't think that the resonant test results would be due to stick slide as the velocity of the stylus in the groove would still be very high when looked at on the scale of the stylus/groove. Could you point me in the direction of the thread LD mentioned, it may give some extra insight.
The method does seem reasonable. It's effectiveness would be maximised if the bearing is of a low friction design and the platter heavy as the rate of slowing would be slow and the resonant peek more accurately determined.
Normally I would agree that mechanical linear tracking arms are better suited to low compliance cartridges. I am, however, getting superb results using a highish compliance cartridge, 22um/mN in my mechanical linear arm. Having said that I am using bearings with level of friction closer to that of an air bearing than that of any ball race bearing. It would be interesting to hear how my arm sounds with a medium compliance cartridge.
Hi Niffy,
I trend to think that speed and friction doesn’t affect arm/cartridge resonance. However, I am going to do some further tests to see what I am going to get.
For your information, the cartridge I used for test was a modified Denon DL-103r. Its compliance is 5 x 10-6 cm/dyne.
The thread LD talked about is here
Turntable speed stabilty
LD is very kind and did two plots for me. He used his amazing software to reveal a lot information we didn’t know. I highly recommend this thread to you.
I bet your linear arm has very low friction so high compliance cartridge can perform well, too. On my old ball bearing arm, 15 is probably the highest compliance it can handle without introducing distortion.
I will post more test results later on.
Jim
I trend to think that speed and friction doesn’t affect arm/cartridge resonance. However, I am going to do some further tests to see what I am going to get.
For your information, the cartridge I used for test was a modified Denon DL-103r. Its compliance is 5 x 10-6 cm/dyne.
The thread LD talked about is here
Turntable speed stabilty
LD is very kind and did two plots for me. He used his amazing software to reveal a lot information we didn’t know. I highly recommend this thread to you.
I bet your linear arm has very low friction so high compliance cartridge can perform well, too. On my old ball bearing arm, 15 is probably the highest compliance it can handle without introducing distortion.
I will post more test results later on.
Jim
Thanks Niffy.
Regards
Can we can put bias type weight on linear bearing arm to compensate for friction damping ? Like string and pulley on one side with weight.
Regards
I did. When I started to build ball bearing linear tracking arm, I used strings and pullys. But it degraded the sound. I learned my lesson that you should not add anything externally. If you want a good arm, you should improve the functionality of an arm structure.
Jim
Thanks Jim.
I have seen your turntable and niffy's linear bearing arm. Both example of excellent achievement.
Another abstract thought I am having is minutely tilting the whole turntable (Linear bearing tonearm not air bearing) to adjust bias. The weight of tonearm will move in opposite direction. Nothing to be added like strings and pulleys.
Regards.
I have seen your turntable and niffy's linear bearing arm. Both example of excellent achievement.
Another abstract thought I am having is minutely tilting the whole turntable (Linear bearing tonearm not air bearing) to adjust bias. The weight of tonearm will move in opposite direction. Nothing to be added like strings and pulleys.
Regards.
Yes. That can be done if you need it. But not the whole table, you may tilt the arm very slightly. Tilting the arm may cause VTA changed slightly.
Jim