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?



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%


I do not get the calculator to work.

I enter in effective length 233.7, overhang 17.2 and offset angle 22.953° with Löfgren B.

And in the calculations and table it spits out today different offset angle  and overhang than I have entered.

I think that the calculator is totally worthless when it spits out data that is not my offset angle  and overhang. (And it doesn't calculate with the provided indata)

So those that got some output did you look that the indata were used is intact or were there their own made up values from the calculator itself!

Or am I missing something here?

@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.


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. 👍🥳