effective length /mounting distance /overhang

[AJ]

Overhang = stylus tip to bearing spindle center

hope this helps make things clearer for someone  

[RCAguy]

For anyone interested in further exploration of tonearm alignment, you might refer to http://www.lencoheaven.net/forum/index.php?topic=14312.60 and the following page p6 of this thread at http://www.lencoheaven.net/forum/index.php?topic=14312.75.

[c3conv]

I am just new here. How much distance should the stylus tip to bearing spindle center be? thanks

[ecosprog]

I am just new here. How much distance should the stylus tip to bearing spindle center be? thanks

I assume you are talking about ´stylus overhang´, but for what tonearm?

This information for a large number of different tonearms can be found on the Vinyle Engine website.

http://www.vinylengine.com/tonearm_database.php

For the Lenco L75 its 17.1mm.

[h-j-hill]

This has the data (and terminology) for the L75 arm.

[RCAguy]

My advice is to forget about overhang, because it's too hard to measure, and isn't itself an adjustment.  Easier is to measure AND to adjust are 1) tip-to-pivot ("effective length") and 2) spindle-to-pivot.  Adjusing these two dimensions, the difference is automatically the overhang.  The other measurement/adjustment for lowest tracking distortion (not necessarily for the lowest angular error!) is 3) "offset" angle between the cartridge and the tip-to-pivot line.  Only use imprecise paper "protractors" as a check, but prefer the mirror type to avoid parallax error.  If you wish, PM me your three measurements, note which you prefer remain fixed, and I'll reply with the optimal positioning & angle within those limits.  Note that it is often possible to skew the cart to the best angle despite that fixed in a given arm.

[h-j-hill]

The L75 arm allows for two adjustments:
(i)   the vertical tracking angle, by moving the pillar up/down; and
(ii)  the overhang, by moving the cartridge carrier to/fro in the headshell.

The latter can be checked by using the L75 card template/protractor; or the stylus tip can be located 9.3 mm from the inside of the front skirt of the headshell.

 

[RCAguy]

There are problems with the illustrations above: At the top of the thread, the illustration is correct for a straight arm, not applicable for an arm with offset angle.  h-j-hill's 11/21/15 is correct, but complex.  h-j-hill's 11/28/15 is incorrect, as the stylus path radius is not tangent to the "arm axis," but tangent to a line in space through the stylus tip, originating at the pivot.  (Note the two different angles in the complex 11/21/15 illustration.)

Arm alignment has been a source of confusion - it was for me until I finally sorted it out.  When I find it, I'll post a simple (and correct) illustration showing the three salient measurements: pivot-to-spindle, pivot-to-stylus tip (effective length), and offset angle.  Again the "overhang" is merely pivot-to-spindle minus pivot-to-stylus tip.  

[willbewill]

Again the "overhang" is merely pivot-to-spindle minus pivot-to-stylus tip.  

Isn't it the other way around

[wer]

Nitpicker 

[RCAguy]

Yes, of course Malcolm - my bad.  Either way, you get 17mm for the L75, just with a minus sign!  Didn't find my drawing yet, but I'll double check it's correct.  too much disinformation already - I certainly don't want to add to it!

[Wout]

h-j-hill's 11/28/15 is incorrect, as the stylus path radius is not tangent to the "arm axis," but tangent to a line in space through the stylus tip, originating at the pivot.

I don't think there's anything incorrect about Hector's image, he doesn't mention off-set angle in that particular image. Just the axis of the cartridge and the arm axis.

[RCAguy]

Hey Wout, and all.  My quibble with Hector's image is that the path shown for the stylus appears to be that traced by the so-called "arm axis," which for our usual offset-angled arms is not correct.  The correct path would be that in blue below, traced by a radius from the pivot to stylus tip in red, a line in space also labeled "L-effective."  (For illustration, the tracking angle error appears exaggerated.)  The stylus path is not tangent to the offset "arm axis," as Hector's image misleadingly depicts it.  Also note that the "Offset angle" is between the two red lines - between the cantilever axis and the red L-effective radius, not a line through the arm.  And the red cantilever line might not even be the centerline of the headshell, as the cart can be skewed intentionally in the shell to adjust the offset angle.



This drawing illustrates how easy it is to align properly a tonearm of a given offset angle and L-effective (with cart/stylus mounted), where only the Pivot-to-spindle need be additionally specified.  Again, the overhang will follow - trying to measure it is more difficult than the following steps:  1) From the spindle, measure and scribe a circle with radius = Pivot-to-spindle; and 2) center the pivot anywhere on that curve.  Voila!

[RCAguy]

Please forgive that my postings above apply only to separate arms & turntables, not to integrated ones, like the Lenco L75.  [I align separates professionally, and so might not have been helpful above to Lenco owners, and others with integrated turntables.]  For these, the spindle-to-pivot distance is fixed, and the offset angle is more-or-less fixed (I'll elaborate later).  The only easy variable is the effective length, pivot-to-stylus tip, so the "overhang" method of adjustment makes some sense, although it is awkward to measure.  The L75 specs in Hector's first illustration above should have tipped me off, however I glazed over it as cluttered and therefore not clear, and lept to posted my general method.  Note too that I promised in the 11-page LH thread "Tuning phonograph reproduction...capacitive loading & channel balancing" thread http://www.lencoheaven.net/forum/index.php?topic=18231.0 based on my illustrated white paper at http://www.filmaker.com/papers/pap_RM-Phono%20C-load%20&%20balance.pdf and its $30 DIY phono stage, someday to do a paper also on tonearm alignment, so consider my posts on this page the beginning of that project.

The screenshot below-top shows my spreadsheet, based on Löfgren-A (Baerwald), for the fixed 210mm pivot-to-spindle of the L75 with integrated arm, optimizing for lowest maximum total harmonic distortion (THDmax, the red curve) due to tracking error with 12in LPs.  Compared to the “factory” specs, I calculate an improvement by increasing "overhang," from 17 to 18mm, also adding to 1mm greater effective length of 228mm.  The calculations also call critically for ~1º more offset angle, yuksing the cart slightly CW with respect to normal orientation in the headshell.  The resulting THDmax is 0.66%.  As the arm nears two null points, THD becomes progressively lower, approaching 0.00% momentarily at the nulls.  This is the lowest THD I’ve calculated for this length arm, similar to that of a SME3009ii fully optimized for all three specs.  (The best I’ve ever calculated is for my longer 14in Audax, optimized for THDmax 0.40%.)

Following the factory specs more than doubles THDmax to 1.44%, as shown below-bottom.  (Forcing my spreadsheet’s overhang and Pivot-spindle dimensions to add to 227mm without optimizing.)  True, this L75 “factory” THDmax is quite low for a 10in LP cut well shy of the label, <0.5%, also for a few individual album cuts not early and later on each side.  However THDmax is 1% at the beginning of a side, 146mm from the center of the disc, and approaches THDmax of 1.44% toward the end, 60mm from the spindle, just when many recordings reach their peak levels, and distortion is more audible, e.g. not masked by environmental noise, as is the case when playing as background music.  These are my expectations for the L75 as supplied by the factory but with overhang set by the user for 17mm - not optimal throughout a typical LP side.





Other points of interest: the THDmax due solely to pivoted tonearm tracking error, although likely masked by other distortion products such as stylus-groove tracing, allows for greater angular error at the outside groove, where the linear speed is about double the inner groove.  The THDmax for 45rpm, and 10in 78rpm, is worst at the inner groove of a long single, but is reduced by the higher rotational speed.  (16in ETs are relevant only if they'd fit this turntable - that I can't discern.)  I hope this is clearer and more useful - I welcome questions [PM to wake me if I seem to be away].

[Wout]

Robin, check this thread.