Where to find uni din protractor

Tawa, The Mint tractor is made for an specific toneram/ turntable cambo. The Uni Din or other so called 'universal tractors' are average tractors for all purposes. But the difference between spindle dimensions by different turnatables can be considerable. Your hope to find the Uni Din second hand for $100 make no sense to me because for the same money you can get a more pricise tractor for your specific tonearm/turntable combo.

Tawa,
If you want to try an alignment like UniDIN, you can use a two point protractor with similar nulls. The difference between the various alignments for a given arm basically amounts to setting up to different nulls, as explained here:
http://odysseytonearms.blogspot.co.uk/search/label/Formulae

I am sure that if you wish to experiment without spending a lot, it would be possible to use the free Chpratz protractor from VE.

Or, if not that, then have Yip make a Mint for a specific known effective length or mounting distance using given nulls.

The important thing with any protractor is to persevere with trying to obtain the required zero error degrees when the stylus is on the nulls.

Hello John,thank you. There is no great hurry on this,curiosity is simply getting the best of me.

Hi dear John, What a pleasure to read the lecture of a real
professional. I have no idea about possible deviation of the
different spindle thickness by different turntables. Yip
consider them as important for the precision of his Mint
tractor. But he sells them so 'some objective' info looks
also important. Will you be so kind to explain the issue?

Tawa, Google for 'Arche headshell' or 'Archon MC cartridge'
to find all Dertonarms inventions.

Hi Nikola,

Some more boring stuff...

There is an RIAA standard from 1963 (and subsequent later revisions and metrications) which gives the record hole size as 0.286", with a tolerance of +0.001" and -0.002". This means that the hole can be between 0.284 and 0.287 (7.214mm to 7.289mm).

Why should this be? It seems a strange size until you remember that the standard was established in the age of imperial sizes, and the nearest fractional size is 9/32" which is 0.281" (7.14mm). This would have been the nominal size for a spindle, and the records were made to fit neatly on a typical spindle, not vice versa.

If a spindle diameter had been within the range for hole size, the record will be a push fit or an interference fit. It won't drop on or lift off easily.

The spindle should probably ideally be 0.282 +0 and -0.002 (7.11mm to 7.18mm)

From a quick internet survey of measured spindles, typical modern spindle sizes are around 7.1 to 7.2mm ie 0.279" to 0.283". In other words 9/32" +/- 0.002", which might be expected.

So, with regard to protractors, these are small amounts and the effect on set up is minuscule regarding the position of the nulls if the error in position is in that direction - variations in distortion in the hundredths of a percent (ie 0.01%)

For a protractor that uses the Dennesen principle, like the Smartractor/Unitractor, any variation in the overhang direction of 0.1mm would produce an error in offset angle in the order of 0.08 degrees, which, depending on the direction of the overhang variation, can actually reduce average distortion for a Lofgren A IEC alignment.

However all these numbers are tiny and bear no relation to the variation in accuracy normally achieved in practice (with whichever alignment). Usually the overhang is easiest to set and both the Mint and the Uni protractor, make much of how accurately their items are made, to within 0.01mm. So perhaps if you have an arm with a micrometer adjustment for overhang you could perhaps work to those tolerances with patience and time.

However, the restricting factor is usually how accurately the offset can be set, especially on an arm where adjusting the offset also affects overhang. If you get within a tenth of a degree you are an ace. Worrying about hundredths is silly.

Best wishes to you and all Audiogoners for 2015.
John
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