Here is my advice: Find out what geometry your tonearm was built for. (Headshell offset angle will vary according to the length of the tonearm and the geometry assumed by its designer.) Then use THAT geometry for THAT tonearm. Here is why: In a few of my own experiments, I found that using a geometry not envisioned by the tonearm design, as you might expect, results in a need to "twist" the cartridge with respect to the long axis of the headshell; the cartridge will not line up perfectly with the headshell, in other words, if viewed from above looking down. Listening tests suggested that this per se seemed to be a "bad thing". I can think of theoretical reasons why this might be so, but I have no proof. However, to avoid that source of distortion, I say again, use the geometry for which the tonearm was designed. Many vintage Japanese tonearms were designed either for a geometry unique to that company (e.g., SAEC, I think) or for Stevenson (e.g., Dynavector and probably your Lustre and Victor tonearms). It's something like LP equalization; back in the "old days" there was no gold standard, and one company often did equalization differently from another. Nowadays, RIAA and Baerwald seem to rule.
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Thom, I don't "view" it one or the other, either. But my recommendation is based on actual real life experience. At least one other person, reporting on Vinyl Engine, had the same experience. I would not argue that others who do it do not seem to perceive that twisting the cartridge in the headshell per se causes any distortion. Here is my hypothesis for the cause of the distortion: When the cantilever is not aligned with the long axis of the headshell, then forces acting in the vertical direction on the cantilever are unevenly distributed back to the tonearm pivot point.
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Thom, The issue of doing the twist (Chubby Checker, where are you now that we need you?) has most to do with using Baerwald or Lofgren with a tonearm designed for Stevenson. This issue therefore only or mostly comes up with vintage tonearms of the kind that you usually do not deal with. In my case, it’s a Dynavector DV505. To set up the DV505 for B or L, one has to twist the cartridge inward (such that the front end of the cartridge is skewed toward the spindle side of the headshell) quite a bit. And of course, when I use the term "cartridge", I am referring to the cantilever, which is what counts, regardless of the fact that some cartridges do not come to us with precisely aligned cantilevers. Ideally, the cantilever should move in an arc in the vertical plane; it’s possible that when the plane of that arc does not align with the vertical plane described by the tonearm bearing, vector forces on the cantilever would not even out. I actually suspect this is a real issue that may be confined to the DV505 and other DV tonearms, where there are two discrete bearing systems, one vertical and one horizontal at play. In these tonearms, the vertical bearing cannot move horizontally to compensate for such a misalignment of the arcs. Maybe that is why I heard distortion as a result. Maybe it's a red herring for more conventional tonearms.
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Something just occurred to me: Is the offset angle required for Stevenson much more acute than that which is required for Lofgren and Baerwald? I think it's the opposite, because of the aforementioned need to twist the cartridge inward on a Stevenson tonearm aligned for L or B. This would mean that there is more skating force at the null points with these latter two geometries, compared to Stevenson. That would be a point in favor of Stevenson. Just a thought.
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Downunder, I don't think we're really "debating" the 3 curves so much as we are talking about what curve is optimal for what tonearms and why. I recently got very interested in tonearms that have zero headshell offset angle and are designed to be mounted with "underhang", which is to say that the stylus tip does not overhang the spindle; instead it is set short of the spindle such that the tip is on the playing surface when the tonearm is pointed at the spindle. With such tonearms, of which there are only two I think, tangency to the groove is achieved at only one point on the surface of the LP, not two, and the most extreme tracking angle error can reach or approach as much as 10 degrees, at the most inner and outer grooves. (But it's more typically 5 to 8 degrees at worst.) BUT, on the other hand, there is zero skating force at that one null point.
What to do with this information? I have long owned an RS Labs RS-A1 tonearm, which is one of the two commercially available arms that use underhung mounting, that I know about. I always wondered why it sounded so good, despite its other rather gimmicky features. Then more recently, the Viv Rigid Float tonearm came on the market, which also uses underhang. The Viv company likes to talk about their floating bearing, of which I am a bit skeptical, but the arm gets great reviews and is revered in Japan and Europe. I think the reason that the Viv and the RS Labs may punch "above their weight" may be that the skating force produced by headshell offset is more noxious than the skating force that arises due to lack of tangency before and after the null point(s) for any pivoted tonearm. And by extension this suggests that our obsession with minimizing degrees of tracking angle error via headshell offset is possibly unwise.
Does anyone own a Schroeder LT? I rather like that one. |
Sampsa (and Fleib),
Just a few things:
While it does appear from visual inspection that the headshell of the RS-A1 might rotate in order to maintain tangency to the groove, this actually does not happen, because the wires from the arm wand to the cartridge are stiff enough essentially to prevent it from happening. Moreover, the English translation of the designer's white paper suggests that he never intended the headshell to rotate. Rather, he is seeking to decouple the headshell from the arm wand. (This is claimed to be so beneficial that the headshell per se is available as a separate product, which could turn any conventional tonearm with a straight pipe and interchangeable headshell mount into an underhung tonearm.)
With the Viv Rigid Float, if you choose the 7-inch version, then indeed the tracking angle error at the extremes will be about 10 degrees. However, if you choose the 9-inch or 13-inch versions, the max error goes down commensurately. While we were in Tokyo, and I was wrestling with the decision to buy one or not, my back of the envelope calculation was for about 5-7 degrees with the 9-inch version (the one I would buy) and less than 5 degrees for the 13-inch version (which I would not buy because I have no turntables that could mount it at the recommended distance from the spindle, and because I think the 13-inch arm wand raises other issues of effective mass and resonance). It's obvious that the inventor of the arm has run into objections related to the tracking angle error with the 7-inch version (the original sole specification) which led him to create the 9- and 13-inch options. I did not buy one, but the temptation will not go away, because our son lives in Tokyo, and the tonearm (all 3 versions) is on display at Yodibashi Camera in Akihabara. |
Sampsa,
Somewhere I have or had a hard copy. But I will also check my other computer to see if I have an e-copy. It's one of those almost laughable translations from the Japanese, but one can make sense of the main points. I see this problem with my son. He thinks and dreams in Japanese. When he speaks to a Japanese person, he does not stumble for the correct words. He is a real scholar in this area. But if you ask him to translate a document from Japanese to English, I can tell that there is effort required, and it takes time. In the RS-A1 white paper, you would see one claim that does not hold up; the paper states that "side force" (skating) is eliminated by the design, when of course it is not; it is only eliminated at the point of tangency to the groove.
Can you, in turn, point me to a review in which anyone compared two different versions of the Viv, so as to be able to say the 7-inch one was preferable? I did not find that review in my search.
Fleib, Can you explain to me how the RS-A1 tonearm reduces or eliminates torsional effects on the cantilever in the vertical plane? I guess you are referring to its other structural oddity, which is that the unipivot bearing is above the plane in which the headshell operates.
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Chakster, You might consider listening to the Victor tonearm in Lofgren for several weeks. Then re-align for Stevenson (only assuming that the Victor UA7045 is designed for Stevenson), and listen for another few weeks. Then decide which you prefer. A few hours of listening to one alignment is not going to provide sufficient information, in my opinion.
Sampsa, I agree that when an underhung tonearm with zero headshell offset is operating anywhere on the LP surface such that the cantilever is not tangent to the groove, there is indeed a skating force. The only point on the LP surface where skating force is negated (zero) is that one point of tangency. But the apparent excellence of such tonearms, despite the large tracking angle errors that they can produce at the extremes, suggests to me that skating force created by the headshell offset angle necessitated to achieve any of the 3 major 2-point geometries, and maybe the common strategy for introducing anti-skate, may be in some way more pernicious than is the skating force due purely to lack of tangency. That's what interests me.
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Thom, I haven't made any meaningful conclusions in years. Most of my conclusions are inconclusive. However, I do think that if we think we can set up a tonearm within less than an +/-0.5mm margin of error, we are kidding ourselves. By the way also, where did I say that I have any particular allegiance to the Feickert protractor? I also own a UNItractor from you know who in Germany. It's capable of a higher level of accuracy, but it's quite fussy to use. Thus I sometimes use the Feickert when push is coming to shove. I've got no beef with an arc protractor either.
Seems to me that a very slight error in implementing Lofgren A/B or Baerwald, or Stevenson, one that still results in two null points on the surface of the LP, is not going to make a huge difference in one's experience of the sound thus derived. I would be receptive to a contrary argument that is based on science.
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Thom, I am not sure what is your point in the last 3 paragraphs above, except to say that any protractor can give bad results if you don't know how to use it. And I don't think any one of us takes a "buckshot approach" deliberately. I am sure each of us is very meticulous, or at least feels that he has been as careful and precise as eyesight and lighting and the protractor make possible.
Wouldn't it be nice if we found out that underhung tonearms, which demand nowhere near the precision accorded to mounting overhung tonearms, were to become accepted as the superior sounding option?
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Fleib, In defense of the arc type protractor, the converse of your criticism of it is that if the P2S distance is not precisely correct, the arc type will tell you that, and you can fix the problem. Whereas the Dennesen and related types don't tell you that with as much precision and certainty. I have an original all-metal Dennesen, which I never use, since I greatly prefer both the Feickert and the UNItractor from Dertonearm. One reason I went away from it is the near impossibility of seeing either the tiny dimple into which the stylus must sit and the grid lines for aligning the cartridge body. They are SOOO faint. It was never easy to use, even in my yout', when I could see real good.
Barbapapa, After only one day, is it not a little bit premature to conclude that you will live forever more with the Lofgren B alignment? I myself am not given to love at first sight, which is why I ask. For one thing, had you auditioned the very same LPs using your old alignment, just prior to the latest re-alignment? Nice stuff, by the way.
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Pryso and other Dennesen aficionados: The UNItractor is kind of a super duper Dennesen. Dertonearm was obviously a fan of the Dennesen, but what he has done is to deal with its shortcomings by providing (1) interchangeable spindle mounts, so that there is zero play at the spindle, which is a source of error when the hole in the protractor is greater in diameter than the spindle, (2) provide separate templates for each and every tonearm, kind of like Mint does with their arc protractors, (3) provide a formal lighting and magnification system which makes it MUCH easier to be exact, and (4) provide an adjustable mainframe which further specifically adapts the device to the particular tonearm you are using. (A booklet comes with the beautifully boxed device telling you what adjustments to make depending upon tonearm, using a built-in micrometer.) Yes, it's fussy, but if you want to be fussy, this is the tool.
So, if you like the Dennesen, you would like the UNI and its offspring (like the SMARTractor) even more. |
