What is you tonearm’s Maximum Distortion?


I’ve been playing around with different cartridge mounting, as a Grace arm the plinth of my Lenco cannot be mounted at the recommended pivot-to-spindle distance of 222mm (closest it can get is 225mm).


My best figures in theory seem to be:
Max. Tracking Error: 3.51 degrees
Max. Distortion: 1.21 %
Average RMS Distortion: 0.73 %

This is with: P-t-s 225mm; overhang 11mm; offset angle 19 degrees.

What are your figures for your setup?

fusian

Showing 6 responses by intactaudio

@rauliruegas 

Forgot that if you want lower distotion figures then and using Löfgren A alignments its tonearm parameters set up are:overhang  21.58mm and offset angle  24.8°.

Where the maximum error  0.94°   maximum distortion  0.33%  and average distortion  0.22%.  All these for your P2S  225mm.

 You need two additional parameters to make the tonearm/cartridge set up and achieve those figures of lower distortion levels and that I don't gave you and are the null points that are: 80mm. and 126mm. not the one you are using today.

are the three quoted sets of numbers referring to the same setup?  

Like Lew, I am skeptical of the accuracy of the 'calculated' distortion numbers since the whole description is to vague. @nrenter  posted a screen grab to John Ellison's Excel spreadsheet.  which can be found on the Enjoy the Music site. This file has the description below of what the calculated percentage distortion refers to.

   Tracking Distortion (Column D) is based on dividing tracking error by groove radius; this is also called weighted tracking error.  Be advised that these numbers are scaled   so that they represent actual percent tracking distortion at a stylus tip velocity of 10 cm/sec.  In other words, the number 1.0 in Column D represents 1-percent distortion.

dave

@rauliruegas 

Since we are considering the theoretical, your proposed alignment simply looks like Löfgren A if you cheat the inner groove radius to 75mm and the outer groove to 143mm which is not realistic for all but the smallest selection of music.  Distortion at the 60.325mm inner groove point will be a fair bit over 2%

dave

@optimize   in order to enter your desired overhang and offset you need to tick the "custom" option or the program will calculate for the 'standard' alignment ticked.

Also the number you enter into the initial arm length will autofill to the remaining three so make sure the same P2S / EL dot is ticked for all 4.  

For your calculation enter 233.7 in Arm 1 Arm Length and tick the effective length dot for all 4 arms.  Then Click the Arm 1 custom dot and enter your desired overhang and offset angles and the results will compare 'your alignment' to the big three.

dave

@rauliruegas 

It’s only a parameter manipulation

Only a parameter manipulation??? If the parameter manipulation is kept hidden then there is another term for it.

dave

 

 

@lewm 

I am skeptical in using the calculated number for anything other than crude relative comparisons and find the plots to be much more telling of the relationships at hand. Below are the plots for the table @optimize posted above.  From looking at the table the Löf B sure looks appealing but the plots tell a different story if you are at all concerned about the last track on an original Blue Note.

 

for reference, here are the plots of the "low distortion parameter manipulated" alignment @rauliruegas posted.   When using a similar alignment I have found no point in listening to the last track or two of a side.

 

I have found that that the traditional 2X weighting factor is not representative of what I hear and that the weighting should be more like 4X. It seems you really need to cheat things to the inner groove closer to Stevenson to get a full side of high quality reproduction.  The last little tidbit is in general the numbers from these charts need to be multiplied by a factor of 5-10 to actually be representative of a real world measurement.

dave

@rauliruegas 

Well, don’t tell to me but directly to the SAT designer.

I do not have an issue where mark sets his null points and I do not believe he would fudge the inner groove radius to 75mm in the calculations to avoid showing the sharp increase in distortion once you get closer than 75mm.

 The OP P2S 225.. was asking for better numbers and the SAT ones gaves it.

Sure... if you use a little harmless parameter manipulation and substantially shift away from a standard set of inner/outer groove numbers you can get vanishingly low numbers.  

" I have found no point in listening to the last track ... "" that's at least untrue because the higher distortion happens only with the LP that has groove modulations  up tp 60mm ( inner groove )

This is akin to saying that a silent groove has no distortion.   JR @wallytools makes a compelling argument and has collected data to support a trend in newer records and audiophile reissues to basically leaving the last track off each side to avoid the issues with the inner groove.  He offers a protractor with dual alignments to take this into account and makes it very clear what his goal is.  The key here is he gives all of the information and lets the end user select what best fits their listening style.  Taken to the extreme I could even see a second arm being added to a setup to allow for two different alignments to match JR's observations.

Btw, have you an alignment with no trade-offs?

Nobody does.  I actually believe that there are far too many variables that cannot be set accurately enough to get any specific alignment and simply getting two null points on the playable surface is no small task.  I want to be clear that I am not being critical of anyones alignment goal.  Everyone is allowed their own choice of compromise.  My problem is presenting manipulated numbers without disclosing the manipulation to justify someones choice.

 

dave