Why use a super accurate cartridge protractor

Dear John, When I stated in some thread that I am hardly
able to see 1mm I got an reprimand from Dertonarm. My compliments for your eye and capabilty to handle fractions of an 1 mm. But if the spindle variations are > 1mm (I forget what Yip from Mint tractor told me) then what is the sense of aiming at 0,2 mm elsewere? Ie some tractors must be more precise then other.

Regards,

Dear Nikola, spindle diameter variations are usually between 7,00 to 7,25 mm - so we are talking derivations between spindle diameters of maximum 0.25 mm.
As long as one tries to be as precise as possible in as many parameters as possible, it is at least a suitable way to get close to a precise alignment.
If the inaccuracy however builds up and adds ever more with the number of parameters "not cared that much about", one may (not need to - by dump luck) get not an alignment, but a "guess" which may be way off.

Why use a super accurate protractor?
Simply because it helps to get the best (read: best sonic performance) out of your cartridge/tonearm.
Would you use an expensive high performance Porsche or Mercedes (Audi, Jaguar - extend at wish ...) with old worn tires suitable for a 1955 beetle?
Not using an as precise as possible alignment ( = super precise protractor ) is simply giving away possible sonic quality and putting the whole performance of one's audio set-up at risk (sonic wise).
It is as easy as that.
If one doesn't really care about sound and possible wear of his/her records - fine, no problem (at least not mine).
But then the question arise why spending hundreds and thousands of dollars for analog playback at all?
CD-players are cheap to get and don't need a protractor (at least not a super precise one ...).
Cheers,
D

Dertonarm,

Löfgren just used euclidean geometry.... He was however unquestioned the first to muse and care about giving phono playback an optimized geometric solid basis.

As you say DT, thankfully we can stick to Euclid and don't have to concern ourselves with Riemann. Re primacy, I believe it was Percy Wilson who published the first analysis of offset tonearm geometry and Loefgren accounted for the factor of decreasing radius as a contribution to distortion. As you say, "every analog audiophile should be grateful for his attempt."

I agree when you say

his preferences and weightings aren't as universal applicable as they were in 1934/38.

My point was simply that the weightings for skewing the tracking error equations
haven't changed. What has happened, as you are well aware, is that we can now easily change the input parameters to the same good old equations and find, as you have done, an alignment that is preferable, and then specify appropriate nulls. But these nulls are not related to the actual inner radius of the records, that is, there is no formula that I have seen published, where I can enter an actual inner and outer radius and come up with say, Uni IEC, or any other null based alignment.

John

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John_gordon, no so far there isn't a new formula.
But then - is there really a need for one?
Given the wide variation in records grooved radius, there is no "royal device"/Königsweg.
The user/operator/analog enthusiast ultimately has to choose the alignment he/she (it..?) prefers.
This choice should be based on the majority of the records in one's collection.
Lucky audiophiles out there with multiple tonearms at hand (Halcro?, Nandric?, Downunder?, Thuchan? ..) might go the way of using different alignments and thus serving all the different records - each with the best suitable alignment.
"My" preference is based on the majority of my collection (mostly US and british records pressed in the late 1950ies to early 1970ies - many with very short dead wax/lead out groove) my preferences in sonics (big and detailed soundstage and up-front, dynamic live-like sonic "picture") AND finally my experience that 0.8% distortion in the lead-in groove are far less sonically "obstructive" (in the negative aural sense) as they are close to the inner label.
Add to that my addiction to big symphonic music, opera and 1950/60 Jazz with many big crescendi towards the end of movements and I have yet another good reason for trying to reduce/minimize distortion in the last 2/3 of the groove.
This of course would in no way apply to a collection of 1990ies to 2010s modern audiophile records where the groove quite often doesn't even come close to IEC inner limit.
I am quite happy that we have a selection of different alignments to choose the appropriate for each collection/preference.
In any case - off now for holiday till mid-september.
Kind regards to everyone and a sunny august!
D.

Dear Nikola,

I find it harder to see (and hear) things as time marches on. But I try.

As you say, the protractor is only as good as the widest tolerance. Which is my point. As DT says, spindles vary, by 0.25mm. So there we actually have a number. But he asks

Why use a super accurate protractor?
Simply because it helps to get the best (read: best sonic performance) out of your cartridge/tonearm.

So super accurate means that "best" is sonic performance, as opposed to physical performance.

In other words to continue DT's analogy, if Michael Schumacher could drive his Ferrari with the old beetle tyres faster than Dertonarm using the expensive ones, then are his tyres better than DT's? Would we buy them?

Wouldn't we rather look at the description of the tyre's performance? The reasons we might choose it for a Ferrari, why it might be suitable.

The analogy here is to the protractor's performance. How accurately can it set up the arm. Will it be within 1mm, 0.5mm, 0.1mm in overhang? Will it be within 1degree, or 0.5, or 0.1? Mounting distance? And how repeatable is it?

I'm not saying Dertonearm's protractor isn't precisely made, or can't give good results, just that neither he, nor anyone else, gives a specification for protractors, one of the few areas in hifi where that is the case. If it was an amp, would manufacturers get away with saying how loud it goes depends on how well you set the volume control?

Perhaps if someone said it was precisely made? Or said it looked impressive?
Or maybe I'm getting too old and too cynical.

John
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