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Time to choose: Baerwald, Lofgren, Stevenson ?

I’ve managed Dr.Feickert Analog Protractor for a decent price (build quality is superb, such a great tool).

Time to play with Baerwald, Lofgren, Stevenson alignments on my Luxman PD444.
Need advice from experienced used of the following arms:
Lustre GST 801
Victor UA-7045
Luxman TA-1
Reed 3P "12
Schick "12

Baerwald, Lofgren, Stevenson ? What do you like the most for these arms?
Manufacturers recommend Baerwald mostly. 

Dedicated "7 inch vinyl playback deserve Stevenson alternative, maybe?
Since it's a smaller format than normal "12 or "10 inch vinyl, it's like playin the last track's according to position of grooves on '7 inch (45 rpm) singles. RCA invented this format, i wonder which alignment did they used for radio broadcast studios.   

Thanks

chakster
sampsa55
71 posts
 
I wasn't referring to a test, but to Baerwald's math models where he derives the distortion resulting from the stylus being at at angle to the groove and the results show the 2nd harmonic dominates. I don't have Loefgren's original paper, so I don't know if the result is even older. (Stevenson wrote his in 1966.) I'm sure it has been tested too.


sampsa55
71 posts
 
Found the Löfgren article from 1938 (and a more recent translation from German to English).

One key assumption Löfgren made in calculating the distortion is that the lateral stylus tip velocity is 10cm/s. It seems others followed this assumption and for instance the Ellison Excel sheet is based on it. This will scale all the calculations and hence is key in understanding the magnitude of the problem. This assumption was made in the time of 78s without RIAA correction, so I’m wondering about the extent that it’s still valid.

Here’s the quote in Löfgren (p. 355):

Die Schnellenamplitude überschreitet wohl selten 10 cm/s (11), entsprechend einer Lichtbandbreite (12) von etwa 25 mm.

The citations (11) and (12) are:

(11) H. J. von BRAUNMüHL und W. WEBER, Einführung in die angewandte Akustik. Leipzig 1936, S. 106.

(12) G. BUCHMANN und E. MEYER, Eine neue optiselle Meßmethode für Grammophonplatten. Elektr. Kachr.-Techn. 7 (1930), H. 4, S. 147—152.



Just came across Gilson’s 1981 article in Wireless World that is quite interesting. I’ll just leave these quotes here without any comment (p. 61):

It shows simply that the lowest possible tracking angle errors can be achieved only at the cost of increasing the values of F and t; and conversely forces F and t can only be reduced by accepting increased angular errors. In the absence of published information on the audible effects of the opposing factors, the optimum balance is anybody’s guess, but it is hard to see justification for the assumption that the lowest possible angular error must necessarily be the best condition.

In thinking about these problems, it is necessary to keep a sense of proportion; tracking error is only one source of distortion and possibly a minor one. Probably the worst source is tracing error, which can easily run into double figures percentage at the inner grooves, particularly with slight stylus wear. Then there is vertical tracking angle error, which is difficult to avoid. Another source is that due to any longitudinal compliance in the stylus/armature system; it is usual to mount the cantilever in an elastomeric grommet or block, and this is not adapted to providing much rigidity in the longitudinal direction.



lewm
6,770 posts
 
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.
fleib
1,124 posts
 

Lewm,

If the RS-A1 headshell doesn't rotate, then the only other unique feature the ViV brings to the table is the floating pivot. I'm not sure how significant this is, but I suspect you already have the better sounding arm. If the goal is to reduce torsional affects on the cantilever, your RS-A1 also does this in the vertical plane which might be more important than lateral. Vertical angular error is more noticeable and more readily heard, IMO. This might also apply to vertical torsion?

I've read a couple of reviews about the ViV and they both said the 7" arm sounds best. Conjecture was, this is due to reduced resonances. It's a little hard to imagine how 10° alignment error could sound better than a lesser value, but conventional wisdom doesn't seem to work here and it would be interesting to compare these two to the Grado Signature.  That one has vertical displacement and an SME type headshell with conventional alignment.


http://www.vinylengine.com/turntable_forum/gallery/image_page.php?album_id=1572&image_id=8766

Regards,


sampsa55
71 posts
 
Lewm:

I've been looking for that RS-A1 white paper. Do you have a link to it?


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