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 4 responses by optimize

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?

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

0.5

 

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. 👍🥳 

As we see here in the graph below 👇

The Löfgren B has lower distortion all over the record surface except in the end just before lead-out starting. But we also know that a 12" LP always start at the same diameter but the 60 mm at the lead-out is something that they recommend that we stop to cut information closer to the label than those 60mm. The issue and problem is to:

1. Find appropriate track to put as the last one. On that A/B side. When the resolution is lowest there.

2. Because of the above we would like to make so that side A and B ends at the same radius. In other words it is not wise to end one side at ~80/90 mm and the other side at 60mm. If we could rearrange the track order so both of the sides end at 70 mm instead. For better fidelity.

3. Many 12" 45 rpm ends further out than 60mm and has a big area lead-out.

4. Do we push the envelope to go closer to the label than 60mm then we get issues with some auto stop or automatic return mechanisms in automatic TT.

So in short lead-in is more or less always at the same place but the same can not been said regarding lead-out, it is far from all 12" discs that end at 60mm when many ends future out for some of the reasons above. With that insight it is less of importance to optimize at just 60mm like Stevenson do in the graph below.

 

It seams that the consequences and penalty for having that aim is that having the lowest distortion from 60 to 65mm (were Löfgren B crossing Stevenson) is that Stevenson has higher distortion then Löfgren B from 65 mm and more or less the whole way until the start and lead-in of the disc!

That is a high price to pay and is only benefits if you has overture 1812 with canons at the end between 60 to 65mm or bolero and other crescendos in that area in many of your favorite albums may have.

 

Otherwise Stevenson is in my opinion something nobody should use. And maybe there is a reason why Lofgren calculated and created a second and improved version after his first attempt.

 

Graphics from previous post.

 

Here we see that this record side is actually close to 60mm:

And as you see it is those 5mm I "sacrifice" with my Löfgren B:

60 to 65 mm that Stevenson has the lowest distortion

 

So it is not a huge "sacrifice" if now the lead-out starting at 60mm.

Or in other words someone that prefer those 5 mm to have the LOWEST distortion on the record has actually "sacrificed" and choose a higher distortion from those 65mm and the whole way to the start of track one!

Thanks @wallytools ! You guys are doing a great job.

Yes, there is most likely bigger fishes to fry than select a alignment but we need one anyway so why not select one of the better ones.

But it is something that we can do easily. And by understanding what they’re bringing to the table makes it simpler to choose the correct one when knowing their strengths and weaknesses from our priorities.

 

The zenith error is baffling that the 3 different mounting companies that mount the diamond to the cantaliver is having that low precision!

Here we go and have different inventions of stylus diamond advance shapes that has very small cutting to make those shapes and ridges.

It feels that we have a made a very beautiful and precise part the diamond and then we have a cantaliver that is tapered aluminum, boron or other highly refined material.

Then we take those two parts and ask someone that has not the understanding of their beauty and precision made parts and their importance of their alignment when gluing them together as a whole unit. I mean it feels that it is not done with the proper care and attention that those parts deserve or with the same precision as they were crafted.

Keep up the good work and hopefully cartridge manufacturers start to put higher requirements on those manufacturers because their tolerances you have uncovered to the public is not doing their products and efforts any favors.💞