straight vs curve
I am not suggesting vintage arms can outperform modern arms. Although some can work really well. But all modern tonearm designs came from somewhere, built on former ingenuity. You're pursuing perfection, which is understandable as an audiophile. I just enjoy learning about different designs as a form of intellectual pursuit and observing this history of them. I actually don't have a favorite type of arms as they all can sound good. I owned some arms just to study them and I sold them once I absorbed their ideas and I just moved on. In that sense I don't qualify as a perfectionist audiophile. It's still fun for me as a hobby.
It's easier said than done, otherwise all arms would be parallel trackers. To achieve ideal linear movement in a tonearm is different than pivot movement, some more successful than others. I don't think of pivoting as moving in a curve since the pivot is a point, way easier to move than slides, glides, or rollers. And it provides better mechanical grounding.
I actually don't champion one type over others but I just don't want to deal with air pumps. There are certain pivot arm rituals I just don't want to give up such as finger-lifting the headshell over the record. And the most annoying of all, having a hovering structure over the platter. I am simply thinking as a user, not knocking the concept.
I owned its predecessor Audiocraft, a unipivot arm that inspired the Graham. While low friction and delicate sounding, its azimuth rocking instability affects its bass performance. I do appreciate unipivot bearings so I like the advancement of using a secondary bearing to stabilize the axial movement. That's a different topic.
I'm glad you are openminded enough to try a different design. I look forward to seeing the results. I have been thinking about parallel tracking arms myself so it will be interesting to learn new possibilities.
I am not suggesting vintage arms can outperform modern arms. Although some can work really well. But all modern tonearm designs came from somewhere, built on former ingenuity. You're pursuing perfection, which is understandable as an audiophile. I just enjoy learning about different designs as a form of intellectual pursuit and observing this history of them. I actually don't have a favorite type of arms as they all can sound good. I owned some arms just to study them and I sold them once I absorbed their ideas and I just moved on. In that sense I don't qualify as a perfectionist audiophile. It's still fun for me as a hobby.
It's easier said than done, otherwise all arms would be parallel trackers. To achieve ideal linear movement in a tonearm is different than pivot movement, some more successful than others. I don't think of pivoting as moving in a curve since the pivot is a point, way easier to move than slides, glides, or rollers. And it provides better mechanical grounding.
I actually don't champion one type over others but I just don't want to deal with air pumps. There are certain pivot arm rituals I just don't want to give up such as finger-lifting the headshell over the record. And the most annoying of all, having a hovering structure over the platter. I am simply thinking as a user, not knocking the concept.
I owned its predecessor Audiocraft, a unipivot arm that inspired the Graham. While low friction and delicate sounding, its azimuth rocking instability affects its bass performance. I do appreciate unipivot bearings so I like the advancement of using a secondary bearing to stabilize the axial movement. That's a different topic.
I'm glad you are openminded enough to try a different design. I look forward to seeing the results. I have been thinking about parallel tracking arms myself so it will be interesting to learn new possibilities.
I finally got the part. All ball point bearings work extremely well. Here are three videos to show you how good the bearings are.
IMG 2882 - YouTube
IMG 2883 - YouTube
Assembled arm
IMG 2886 - YouTube
I applied Loctite Thread Locker Blue 242 to all the set screws and highly recommend anyone who uses set screws as bearings to do so. The thread locker gives me great control with set screws.
The first thing I will do is to test the skating as it is the original purpose of this arm. Then, I will wire it up to have a listen.
IMG 2882 - YouTube
IMG 2883 - YouTube
Assembled arm
IMG 2886 - YouTube
I applied Loctite Thread Locker Blue 242 to all the set screws and highly recommend anyone who uses set screws as bearings to do so. The thread locker gives me great control with set screws.
The first thing I will do is to test the skating as it is the original purpose of this arm. Then, I will wire it up to have a listen.
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I did the skating tests on the arm.
I thought the arm was not going to skate at the beginning. But everyone said that the arm would skate. Later on, I tended to agree with everyone. However, the test is a surprise for me. Here is the video. The arm doesn't skate.
No Skating - YouTube
I suspected that there might be a side force to act as an anti-skating force. So, I added more counterweight without touching anything else. The cartridge hovered over the record. From the video, you may see that the cartridge kept balance without moving to the side. The only movement happened at 1:20. The cartridge hovered over the edge of the record. The arm moved toward the opposite direction of the center of the record. It was potentially an anti-skating force.
No Side Movement - YouTube
For this kind of arm, the level of the arm base has a great impact on the operation of the arm. Here is another case in which the side force did exist. The side force was created by adjusting the level of the base. I realized the importance of the level of the base and installed three set screws to adjust the level of the base.
Video shows the toward the center of the record.
Side force - YouTube
Therefore, skating existed.
Skating with side force - YouTube
Based on the tests, the conclusion should be if the side force exists, the arm skates. The arm itself does NOT skate.
Am I confident enough to accept the conclusion? Tell you the truth. I am not sure. However, this is what the tests show us.
I thought the arm was not going to skate at the beginning. But everyone said that the arm would skate. Later on, I tended to agree with everyone. However, the test is a surprise for me. Here is the video. The arm doesn't skate.
No Skating - YouTube
I suspected that there might be a side force to act as an anti-skating force. So, I added more counterweight without touching anything else. The cartridge hovered over the record. From the video, you may see that the cartridge kept balance without moving to the side. The only movement happened at 1:20. The cartridge hovered over the edge of the record. The arm moved toward the opposite direction of the center of the record. It was potentially an anti-skating force.
No Side Movement - YouTube
For this kind of arm, the level of the arm base has a great impact on the operation of the arm. Here is another case in which the side force did exist. The side force was created by adjusting the level of the base. I realized the importance of the level of the base and installed three set screws to adjust the level of the base.
Video shows the toward the center of the record.
Side force - YouTube
Therefore, skating existed.
Skating with side force - YouTube
Based on the tests, the conclusion should be if the side force exists, the arm skates. The arm itself does NOT skate.
Am I confident enough to accept the conclusion? Tell you the truth. I am not sure. However, this is what the tests show us.
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I repeated the same process again. This time the arm didn't skate even close to the end of the groove.
No skating 2 - YouTube
No side force 2 - YouTube
Again, you may see if the arm skates, it is caused by side force, which is the result of imperfect leveling. If the base is perfectly leveled, the arm won't skate.
I even made a video to show outward skating under particular leveling. You can see the arm skates outward and finally it dropped off the table.
outward skating - YouTube
It also reminds me that if I build another version of PT arm, I need to incorporate a mechanism to precisely level the base.
It further tells me that for Reed 5A arm, and other similar arms, they will skate or won't skate depending on the setting of the table you are going to install on. The arm itself doesn't skate by itself. It sounds messy to me.
No skating 2 - YouTube
No side force 2 - YouTube
Again, you may see if the arm skates, it is caused by side force, which is the result of imperfect leveling. If the base is perfectly leveled, the arm won't skate.
I even made a video to show outward skating under particular leveling. You can see the arm skates outward and finally it dropped off the table.
outward skating - YouTube
It also reminds me that if I build another version of PT arm, I need to incorporate a mechanism to precisely level the base.
It further tells me that for Reed 5A arm, and other similar arms, they will skate or won't skate depending on the setting of the table you are going to install on. The arm itself doesn't skate by itself. It sounds messy to me.
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Birch genre
Thanks for all the videos and demonstrations, Jim!
There's a very slight skating inward at 0:07 mark at the needle drop and then becomes skateless. It is very slight so perhaps it's inconsequential. Judging by these videos that whatever theoretical skating force may exist, in practice it might not be enough to affect the sound or operation negatively, unlike a traditional pivot arm. And to me that's actually an encouraging sign.
I think having the main horizontal arm pivot close to the Thales locus is the right decision, unlike the Garrard Zero or Thales Simplicity, which all skate like typical pivot arms and use an anti-skating device. The group of arms that I loosely term them the "Birch" genre or Birch style arms (a la Schroeder LT, Reed 5a, Thiele TA01, Trenton Jacob's Ladder ,Tuthill, and JW 6B ) they all used no anti-skating.
It actually renews my interest in the Birch strategy. I think you're right about getting the vertical arm to be as short as possible from a structural standpoint but it also conflicts with the need to have the fixed pivot position to be as close to the Thales locus. I believe there' might be a hybrid arrangement somewhere, a sweet spot. Hmm...
I think ALL tonearms benefited from perfect leveling, be it a pivot arm or parallel tracker or multi-linkage arm, unless it's employed strategically to "lean" one side or other to counter an unwanted force. A Birch style pivot tangential arm is just more critical than others. Because it has multiple linkages, the unleveled leaning side force is amplified by each linkage.
= = = = = = = = = = =
Whatever conclusion you will draw from this, I appreciate the time, expense, and effort you put into building this arm for all of us to see. Thank you, Jim!
Thanks for all the videos and demonstrations, Jim!
There's a very slight skating inward at 0:07 mark at the needle drop and then becomes skateless. It is very slight so perhaps it's inconsequential. Judging by these videos that whatever theoretical skating force may exist, in practice it might not be enough to affect the sound or operation negatively, unlike a traditional pivot arm. And to me that's actually an encouraging sign.
I think having the main horizontal arm pivot close to the Thales locus is the right decision, unlike the Garrard Zero or Thales Simplicity, which all skate like typical pivot arms and use an anti-skating device. The group of arms that I loosely term them the "Birch" genre or Birch style arms (a la Schroeder LT, Reed 5a, Thiele TA01, Trenton Jacob's Ladder ,Tuthill, and JW 6B ) they all used no anti-skating.
It actually renews my interest in the Birch strategy. I think you're right about getting the vertical arm to be as short as possible from a structural standpoint but it also conflicts with the need to have the fixed pivot position to be as close to the Thales locus. I believe there' might be a hybrid arrangement somewhere, a sweet spot. Hmm...
I think ALL tonearms benefited from perfect leveling, be it a pivot arm or parallel tracker or multi-linkage arm, unless it's employed strategically to "lean" one side or other to counter an unwanted force. A Birch style pivot tangential arm is just more critical than others. Because it has multiple linkages, the unleveled leaning side force is amplified by each linkage.
Is that a sonic evaluation or a criticism of the leveling procedure?
= = = = = = = = = = =
Whatever conclusion you will draw from this, I appreciate the time, expense, and effort you put into building this arm for all of us to see. Thank you, Jim!
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Aside from imperfect levelling or bearing friction/stiction issues, there is a skating side force component from the geometry of the arm, even though you have convinced yourself that there isn’t.
The good news is that the skating force appears to be insignificant compared to the side force(s) resulting from the base not being level. The bad news is that slight mis-leveling of the base creates significant side forces.
It also appears from watching the videos that bearing friction/stiction is insignificant compared to the side force(s) resulting from the base not being level. Here too, the effects of bearing friction appear to be swamped by the side force(s) resulting from base mis-levelling.
Frank Schroeder exploits the side force(s) arising from the mis-levelling effect in the design of his PLT and uses it as one of the measures to compensate for the skating force that “stems from the overall geometry” of his arm.
https://www.diyaudio.com/forums/ana...angential-pivot-tonearms-210.html#post5867627
The design of his base allows for levelling and intentionally “vertically offsetting the main bearing by the correct amount and in the right direction (180° to the stylus drag vector)” to cancel the skating force resulting from the geometry. The trick is knowing how much to mis-level and in what direction. I don’t see that in his patent and assume that that know-how is in the realm of “proprietary”. You may have found such a balance in your experimentations.
The proof of the pudding will be posting a YouTube video of a head-on view of the cartridge while playing a real record and dealing with eccentricities et all to see if the arm follows the groove without any cantilever deflection.
Your arm certainly looks impressive.
Ray K
The good news is that the skating force appears to be insignificant compared to the side force(s) resulting from the base not being level. The bad news is that slight mis-leveling of the base creates significant side forces.
It also appears from watching the videos that bearing friction/stiction is insignificant compared to the side force(s) resulting from the base not being level. Here too, the effects of bearing friction appear to be swamped by the side force(s) resulting from base mis-levelling.
Frank Schroeder exploits the side force(s) arising from the mis-levelling effect in the design of his PLT and uses it as one of the measures to compensate for the skating force that “stems from the overall geometry” of his arm.
https://www.diyaudio.com/forums/ana...angential-pivot-tonearms-210.html#post5867627
The design of his base allows for levelling and intentionally “vertically offsetting the main bearing by the correct amount and in the right direction (180° to the stylus drag vector)” to cancel the skating force resulting from the geometry. The trick is knowing how much to mis-level and in what direction. I don’t see that in his patent and assume that that know-how is in the realm of “proprietary”. You may have found such a balance in your experimentations.
The proof of the pudding will be posting a YouTube video of a head-on view of the cartridge while playing a real record and dealing with eccentricities et all to see if the arm follows the groove without any cantilever deflection.
Your arm certainly looks impressive.
Ray K
DD,
Yes. Brich geometry arm seems like a plausible option for a linear arm.
1, No tracking errors. My 6B arm has a 185 mm arm. Its maximum tracking error is less than 0.1 degrees. My 6C has a 60 mm arm. Its tracking error is even smaller. These tracking errors are neglectable.
2, No skating. This may be the biggest reason to build a Brich geometry arm.
3, Efficient bearing. There are still no efficient bearings for the linear arm. My v-groove linear arm bearing may have great potential, but it is not a reality yet. A ball pen pivot bearing is cheap and very efficient.
4, Short arm without complicated retrieving system. A linear arm needs a retrieving system to utilize a short arm.
I agree that all tonearms benefited from perfect leveling. However, Brich style arm is especially sensitive to the leveling.
I said, “it sounds messy to me”. I meant for regular users of these arms, they may just adjust the level of the table based on the indicator of a bubble level. It is far from accurate. A turntable is not so sensitive to leveling. So, a Brich style arm may act differently. For some, the arm may skate inward. For some, the arm may skate outward. Of course, some may not skate. All these commercial Brich style arms don’t have the mechanism to adjust micro leveling. It may be a problem for users while they are not even aware. A bubble level is just a rough indicator. It is not enough. This is why I said it is messy.
Jim
Yes. Brich geometry arm seems like a plausible option for a linear arm.
1, No tracking errors. My 6B arm has a 185 mm arm. Its maximum tracking error is less than 0.1 degrees. My 6C has a 60 mm arm. Its tracking error is even smaller. These tracking errors are neglectable.
2, No skating. This may be the biggest reason to build a Brich geometry arm.
3, Efficient bearing. There are still no efficient bearings for the linear arm. My v-groove linear arm bearing may have great potential, but it is not a reality yet. A ball pen pivot bearing is cheap and very efficient.
4, Short arm without complicated retrieving system. A linear arm needs a retrieving system to utilize a short arm.
I agree that all tonearms benefited from perfect leveling. However, Brich style arm is especially sensitive to the leveling.
I said, “it sounds messy to me”. I meant for regular users of these arms, they may just adjust the level of the table based on the indicator of a bubble level. It is far from accurate. A turntable is not so sensitive to leveling. So, a Brich style arm may act differently. For some, the arm may skate inward. For some, the arm may skate outward. Of course, some may not skate. All these commercial Brich style arms don’t have the mechanism to adjust micro leveling. It may be a problem for users while they are not even aware. A bubble level is just a rough indicator. It is not enough. This is why I said it is messy.
Jim
Ray,
All the videos provide evidence to support the following points.
A Brich style arm, at least for the 6B I build, doesn't skate. There is no skating force generated from its geometry.
Its leveling is critical for operating the arm correctly.
You don't need to compensate for skating by mis-leveling since there is no skating at all. If you want to compensate for skating by mis-leveling, you are actually creating the skating force. Almost everyone thinks Brich style arm skates. In fact, it is not.
If Frank is reading this thread as well, you are very welcome to join the discussion. The LT arm has exactly same geometry as my 6B. I can say it doesn't skate either.
Jim
All the videos provide evidence to support the following points.
A Brich style arm, at least for the 6B I build, doesn't skate. There is no skating force generated from its geometry.
Its leveling is critical for operating the arm correctly.
You don't need to compensate for skating by mis-leveling since there is no skating at all. If you want to compensate for skating by mis-leveling, you are actually creating the skating force. Almost everyone thinks Brich style arm skates. In fact, it is not.
If Frank is reading this thread as well, you are very welcome to join the discussion. The LT arm has exactly same geometry as my 6B. I can say it doesn't skate either.
Jim
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leveling adjustment
As a commercial product the Schröder LT does have leveling adjustment as explained by Frank from another thread, quoted below. As you can see in this picture that the base is a 3 point design for micro-leveling with one mounting bolt and two adjustable set screws.
While your arm may exhibit no (or very tiny) visible skating for whatever reason, Frank admits in the quote that his arm allows adjustment to " compensate for any remaining skating force that stems from the overall geometry." So, his LT arm does have small amount of skating.
Perhaps Doug can chime in on this. I wish there's a Dual Skat-O-Meter to verify it. From what I saw the 6B does have tiny amount of skating probably trumped by bearing friction, unleveled side force, and/or various hidden microscopic counter forces, as suggested by Ray.
So, in the end skating becomes moot or insignificant to worry about in practice and certainly miles less than traditional overhung tonearm. That means a Birch style arm is a viable option for tangential tracking. And that's a good news!
As a commercial product the Schröder LT does have leveling adjustment as explained by Frank from another thread, quoted below. As you can see in this picture that the base is a 3 point design for micro-leveling with one mounting bolt and two adjustable set screws.
While your arm may exhibit no (or very tiny) visible skating for whatever reason, Frank admits in the quote that his arm allows adjustment to " compensate for any remaining skating force that stems from the overall geometry." So, his LT arm does have small amount of skating.
Perhaps Doug can chime in on this. I wish there's a Dual Skat-O-Meter to verify it. From what I saw the 6B does have tiny amount of skating probably trumped by bearing friction, unleveled side force, and/or various hidden microscopic counter forces, as suggested by Ray.
So, in the end skating becomes moot or insignificant to worry about in practice and certainly miles less than traditional overhung tonearm. That means a Birch style arm is a viable option for tangential tracking. And that's a good news!
Just a brief comment regarding the compensation of skating force on the LT. There are several ways to compensate for any remaining skating force that stems from the overall geometry, like changing the proximity of the guide magnet vs. the guide rail over its length.
The main reason why you won't experience the arm showing any tendency to move inwards or outwards when either "riding" a blank record or with a Dual skate-O-meter on a modulated record is the fact that the stylus drag can be countered nearly 100%(within the stylus drag/vinyl friction coefficient variation range) through vertically offsetting the main bearing by the correct amount and in the right direction(180° to the stylus drag vector).
The main arm assembly, which sits on a rotating cantilever(so to speak), can be seen as a pendulum and it will seek the lowest position. The base of the LT allows for not just leveling, but ever so slightly off-setting the arm to generate a force exactly opposing the stylus drag, hence avoiding the generation of a skating force. Cancellation would be the proper term here...
And, quite obviously, such an arrangement wouldn't pass the "attach a string and pull along the cantilever"-test as the generated drag will always be far higher than the stylus drag.
Sorry, I missed that.
For my test, the stylus was riding on a blank record.
If the arm skated, I raised the arm by adding counterweight so the arm was suspended in the air. The arm would move inward by itself in the same direction as it skated. The leveling is not right.
If the arm didn't skate, I suspended the arm in the air. The arm would be stationary. The leveling is perfect.
What I am trying to say is adjusting the level is of no use for compensating for skating. The level should be perfect leveling all 360 degrees always no matter what. If you purposely mis-level the base, you are creating a skating force. You are not cancelling the skating force. The only and accurate way to know if the leveling is correct is to suspense the arm in the air and observe its movements. If the arm is stationary, the level is ok. If the arm moves by itself in the air, the level is not correct.
There may be small forces from the pivots or other parts to compensate tiny skating force. I don't know and may never be able to know. But the arm doesn't skate, this is what I can see.
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In order to illustrate my view, I post the videos again.
This is the video shows the arm doesn't skate after I adjusted the level.
No skating 2 - YouTube
I kept the same setting for the leveling but raised the arm by adding counterweight This is the video shows the arm is suspended in the air and is stationary. I had to hit the arm slightly to move the arm.
No side force 2 - YouTube
Both videos above indicate the leveling is perfect all around.
The next video shows the arm skates.
Skating with side force - YouTube
Without re-adjusting the level, I raised the arm by adding counter weight again so the arm was suspended in the air again. The arm moved in the same direction as it skates. The level is not correct.
Side force - YouTube
In other words, first, raise the arm in the air. Then, adjust the level until the arm is stationary. The level is perfect. The arm will not skate.
This is the video shows the arm doesn't skate after I adjusted the level.
No skating 2 - YouTube
I kept the same setting for the leveling but raised the arm by adding counterweight This is the video shows the arm is suspended in the air and is stationary. I had to hit the arm slightly to move the arm.
No side force 2 - YouTube
Both videos above indicate the leveling is perfect all around.
The next video shows the arm skates.
Skating with side force - YouTube
Without re-adjusting the level, I raised the arm by adding counter weight again so the arm was suspended in the air again. The arm moved in the same direction as it skates. The level is not correct.
Side force - YouTube
In other words, first, raise the arm in the air. Then, adjust the level until the arm is stationary. The level is perfect. The arm will not skate.
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No, they are not. They do not prove that that the bearing friction is not simply greater than the skating torque.
Here is another video to show the arm doesn't skate.
no skating 3 - YouTube
It doesn't matter if someone speculates the arm is embedded an anti-skating force or not. It is a simple fact that the arm doesn't skate.
I can make the arm skates by adjusting the level, but I can't adjust the level to generate an opposite force to against the inward skating force. Once I generate an opposite force to against the inward skating force, the arm will skate outward. This is why I said. You can't adjust the level to cancel inward skating force.
no skating 3 - YouTube
It doesn't matter if someone speculates the arm is embedded an anti-skating force or not. It is a simple fact that the arm doesn't skate.
I can make the arm skates by adjusting the level, but I can't adjust the level to generate an opposite force to against the inward skating force. Once I generate an opposite force to against the inward skating force, the arm will skate outward. This is why I said. You can't adjust the level to cancel inward skating force.
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