Uni-Protractor Set tonearm alignment

Once we cannot change the offset FOR the headshell...
...I suppose it is just a number and the only thing that we have to do, is to align the cantilever (by twisting the cartridge AT the headshell) to follow the axis of the tangent at the null point.
This particular tangent, is quite easy to designed by drawing the line from the center of the spindle to the desired null point and then we can easily find & draw the perpendicular of this line that intersects at the null point.
But I think that Daniel wants to provide a precise goniometer at the near future!

Downunder,
I am not so much an expert as a student who is not afraid of Excel. The math is easy. For fun and games, please try this spreadsheet.

Disquisitive Dert's numbers do NOT provide a better mousetrap technically unless you WANT them to. Choice of alignment depends on priorities, not on absolutes. Lofgren B will get you the lowest average whole-record tracking distortion every time. Baerwald will get you the lowest peak whole-record tracking distortion every time. Using other configurations, like Stevenson, or Dert66 or Dert63 will get you a lower average and peak distortion within a specified section of long-playing records (the average of the inner half, and especially lower on peak distortion in the last 1.0-1.5cm or call it the last 2-4min).

As to getting the offset angle set up really accurately, the only real way I can think of to do that is use a high-quality arc protractor (and a good set of eyes) where you can trace the specified arc (the one created by your setup angles), and check tangency of cantilever (or more importantly stylus orientation).

Raul,
I am not too familiar with the VE calculator but I will, for the sake of the first part, assume it is correct. I have just run a set of calculations using your link as a base. If we use Dert63 DIN (246/14.5/20.574) compared to a standard Baerwald or Lofgren B DIN (245mm EL), I get a whole-record average of 0.42% for Dert63 and .433% for Baerwald, and 0.39% for Lofgren B. I get max TD of 0.89% for Dert63, o.66% for Baerwald, and 1.09% for Lofgren B. These are whole record numbers, and as D suggested, the Dert63 curve looks reasonably like the Lofgren B curve except it is displaced closer in.

Note that I use DIN for the calculations because it is obvious from everything that the Doctiloquent Dert has said that he is concerned with records which have smaller inner groove radii than the IEC standard 60.3mm.

These would fit the observations made by the Dastardly Dert. The VE graph cannot be used to approximate "inner two-thirds" with any accuracy. I have just recalculated, using a fresh version of my spreadsheet (which I downloaded from the link above), which shows that Dert63 DIN (246/14.5/20.574) has better average tracking distortion over the inner two-thirds of the record than either Baerwald DIN 245 (33% lower) or Lofgren B (13% lower), and lower max than Lofgren B by about 20% (0.89% max (outer groove) vs 1.09% max (inner groove)). I also get an overall average DIN tracking distortion (vs Baerwald) of about 5-6%, using either Dert66 or Dert63 (the difference shifts the shape a bit inwards, lowering last centimeter peak distortion).

Note to this: my spreadsheet is set up differently than the VE calculator. It would appear that the "Average" distortion on the VE calculator for IEC is calculated using the DIN min/max groove radii, not IEC. I don't see how the VE calculator gets its average tracking distortion for DIN either. I get the same max but my spreadsheet's average is lower (it does not jump nearly as much in the switch from IEC to DIN). Something may be wrong with the VE calculator to jump that much (it is as if the average calculation includes distortion in the un-modulated grooves (55-57.5mm on the graph) but the max stops at 57.5mm). Strange. I will re-check mine but in any case, my calculations would be more conservative than the VE's if it were the case (i.e. the VE calculator would probably show an even stronger improvement by using Dert63 vs Lofgren B than my numbers show).

I hope this helps disembrangle and disculpate the occasionally didactic but certainly dianoetic Dertonarm.

:^)

Dear T-bone: According with Nandric those FR numbers comes from: 1984 German Magazine 'Das Ohr' that I can't find it on the net to read how comes the numbers.

I
Btw, I'm still waiting what I ask you before. Thank you.

Regards and enjoy the music,
Raul.

T_bone: because the last link using the FR numbers with the offset angle you states still shows different distortions numbers to the ones you posted.

Why is this?, I assume you have the answer. Thank you.

regards and enjoy the music,
Raul.

Raul,
I do not understand your question and what you are looking for in your "1984 German magazine" post. I do not know where the Nandric reference comes from. I do not know what "those FR numbers" refers to. If you want to tell me what "those FR numbers" refers to, please do. I also do not know what you are talking about when you say "I'm still waiting what I ask you before" but it may be answered below.

As to your next post, the numbers I posted for Dert63 DIN (246/14.5/20.574) were:

whole-record average of 0.42% for Dert63 and .433% for Baerwald, and 0.39% for Lofgren B. I get max TD of 0.89% for Dert63, 0.66% for Baerwald, and 1.09% for Lofgren B

The link for the Dert63 (20.574mm offset angle) DIN calculation for those parameters on the VE calculator is below:
http://www.vinylengine.com/tonearm_alignment_comparator.php?m_el=246&m_oh=14.5&m_oa=20.574&compare=d&submit=calculate
They state: 0.421% average and 0.89% max.

The link for the 245mm EL (which is nearly the same as the link you provided above - just switched to DIN rather than IEC) is
http://www.vinylengine.com/tonearm_alignment_comparator.php?m_el=245&m_oh=15&m_oa=21.5&compare=d&submit=calculate
They state 0.39% average and 1.09% max for Lofgren B and 0.443% average and 0.661% max for Baerwald.

Those numbers on the VE calculator results linked are EXACTLY as I posted. My assumptions are clearly stated. Dert63 uses 246mm EL, 14.5mm OH, and 20.574 degrees offset angle. The Baerwald and Lofgren B references use the original 245mm EL. All three assume DIN groove radii.

My recent post focuses on Dert63 rather than Dert66, that is to say on the 20.574 degree estimate (i.e. 63mm inner null point), because it gives the 20% lower max than Lofgren B, and 5% lower average than Baerwald that the deipnosophistic Dertonarm mentioned in one of his earlier posts.

If you find different numbers than mine from those links, please show them. I do not see how I can be clearer in my 'proof'. The link to the spreadsheet which would allow you to do the same calculations for average and max distortions over any portion of the modulated groove range (i.e. the inner two-thirds) is provided above.

In any case, it is pretty intuitive. Dert63 is something like a shifted Lofgren B. If you shift the Lofgren B curve towards the center, you will have higher distortion at the outer groove, and MUCH lower distortion in the inner area, and because of the shape of the Lofgren B curve, the average of the inner part will be lower with the shifted version. And as I and others have said, choosing geometry is a matter of personal priorities. The 'absolute' with any of these has to be qualified very specifically.