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?

Parameter Custom Lofgren A Lofgren B Stevenson
pivot to spindle (mm) 216.5 215.96 215.45 218.02
effective length (mm) 233.7 233.7 233.7 233.7
overhang (mm) 17.2 17.74 18.25 15.68
offset angle ° 22.95 23.57 23.57 22.35
linear offset (mm) 91.14 93.44 93.44 88.87
inner groove (mm) 60.33 60.33 60.33 60.33
outer groove (mm) 146.05 146.05 146.05 146.05
inner null point (mm) 67.42 66 70.29 60.33
outer null point (mm) 114.86 120.89 116.6 117.42
maximum error ° 2.25 1.85 2.06 2.24
maximum distortion % 0.77 0.64 1.03 0.77
average rms distortion % 0.38 0.42 0.37



Thanks @intactaudio !

Here is my numbers seams they are pretty good compared to the other's. Using the Löfgren B that is the best on the average for a whole LP. 

I did my custom protractor several years ago and it seems to be OK and the numbers I took from that custom protractor.

So I did this also to check its old calculations. 👍🥳 

@intactaudio : It’s only a parameter manipulation and that is the SAT tonearms alignment. At the end is not rocket science. Btw, Did you already test that kind of alignment?, I do and you can be " surprised " by. 

As Mark SAT designer says and makes sense:  " The null points for the SAT arms are located at 80 and 126mm. Ultimately, this was a choice of enjoying a consistently higher level of fidelity for 95% of the time over having less angular error on 5% of the tracks. "

Exist rules but to each one of us can be broken in favor of quality performance with MUSIC.

That alignmnet by SAT is wrong? no it’s only different and when tested each one of us can decide about. What you think or what I think is only that " think " as is non-important in the whole alignment game: it’s each one game not yours not mine.




It’s only a parameter manipulation

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




If the numbers in the table published here by optimize are correct, two things pop out at me. First, the distortion figures are below 0.5% or equal to 0.5% in all cases. Given all the other distortions inherent to vinyl reproduction, does anyone here think he can hear the difference between 0.5% and 0.3% distortion? second, there is a dissociation between the magnitude of the tracking angle, error, or at least the maximum magnitude of the tracking angle error and distortion. Isn’t that interesting?


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.