Uni-Protractor Set tonearm alignment

Halcro

I haven't used it, but I'm sure you are correct in assuming a different principle for the Feickert. If it has the facility to set or measure mounting distance, it is because it uses arcs which have to be referenced to a known pivot point.

You are correct in saying that headshell type cartridges having no facility for adjustment need to have the effective length of the arm with the cartridge fitted known or measured. Also the true cartridge offset angle (which will depend on the arm/cartridge combination) also known or measured. Then an appropriate mounting distance can be calculated, and precisely set.

Alternatively, using an arm with a known alignment, you can use (if it has the same alignment) a two point protractor to set up. By sliding the base the offset will be given automatically. Swapping different kinds of these cartridges would depend on them having the same headshell mounting collar to stylus distance.

You are also right in saying that swapping headshells could be problematic. It looks to me that swapping headshells between arms would require them to be set up initially with one headshell/ cartridge combination which remained set once the first arm was done, and which was then used to set the remaining arms with adjustment achieved at the bases of the others, assuming they were different arms.

The alignment chosen would have to also be the same for each set up, irrespective of the arm design, but the arms could be different lengths. Then any cartridge/ headshell combination could be set up to suit these alignments without moving the bases. This would depend on the headshells having slots, though the initial headshell could have holes as long as the arm used was designed to the chosen alignment.

I think that covers most of the difficulties..... please feel free to point out a simpler way, any mistakes or anything I've overlooked.

John
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Dear Halcro: My mistake. That 15mm on overhang is not what help me but the distance between the cartridge stylus and the rear part on the headshell that if I remember is 50mm on some of my tonearms.

Raul.

Dear Halcro: I don't think you noted yet. Several of my hedashell removable tonearms design have the manufacturer overhang spec at 15mm, I choosed on porpose due so many tests cartridge/tonearm combinations I have. This similar overhang characteristic help me to mount with almost none change any cartridge in any of those tonearms.

Yes, this is not exactly what you are talking about but an idea that could help.

Btw, now that you and other people are so in " deep " about cartridge/tonearm set up through accurate protractors seems to me adequate for you and every one that want to " explore " and learn on the subject to make a simple ( no money need it.! ) experiment:

- in one or two of your cartridge/tonearm combinations move the cartridge 1mm forward ( no protractor need it. ) and mantain the same cartrridge/headshell offset angle. After re-set the VTF and VTA/SRA and if you want azymuth and antiskate ( not need it for the experiment but if you want to be more " even " with today set-up. ) push the playback " button " and listen for a while.

After that and if you have the time and patience move the cartridge an additional 1mm forward and the same process but moving the cartridge 1mm and 2mm rearward.

Compare what you listened on those four different set ups against each to other and against what you are listening in your rigth now set ups.

IMHO this is a un-expected ( because the quality performance ) experiences where we could learn what is happening down " there ", I mean on playback against no-play status.

All of you that decide to " explore " in this " jungle " will be appreciated what you experienced.

Thank you in advance.

Regrads and enjoy the music,
Raul.

Jazzgene, 'to bad Thorens ain't what it used to be'. I agree but there are many of those 'old one' second hand still demonstrating the value of simplicity in design: good platter, good bearing and an simple motor. Despite of
this fact the Uni-Pro on them looks to me like a King on
a donkey.

Regards,

Dertonarm:

You said:

If a phono protractor really is universal, it must automatically align regardless of the given mounting distance.

I would agree with you in that, but I would disagree with you when you say that

Setting the mounting distance is done before aligning the tonearm. It is a "conditio" already set before starting the alignment.

This is only necessary when using a protractor which requires it - like yours - because, as you say,

The UNI-Pro does follow the smart idea of Francis Dennesen and adapts to whatever P2S a given tonearm is mounted.

As is the case with the Dennesen, arms with adjustable bases and fixed headshell mounts are awkward for your protractor. So it can´t really be called universal, as it only caters for arms with adjustment for effective length and offset at the headshell.

In most cases the tonearm is already mounted when one starts to align the tonearm/cartridge

All arms are "mounted" prior to alignment, but, as you are aware, not all arms have the pivot to spindle distance fixed at a specific measurement, but have the facility to adjust this, as in any arm on a pod or adjustable arm board, or the SME, and arms like it.

It could be argued that a more universal version of the Dennesen would have adapted it to allow its use with arms such as these, as well as with different alignments.

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