The importance of VTA, SRA and Azimuth - pics

[Solypsa]

I don't think the question is whether the ear is better than measurement tools. Rather, you can't do anything about an imprecise zenith alignment unless you know you have one. Do you know if you do or do not?

No issues regarding manufacturing QC. It's inexcusable when you are paying 10K + for a cartridge not to be assured the zenith is spot on.

I get what you are saying, and agree all parameters should be on a tight tolerance for high end carts. That said nothing is perfect and there is always a tolerance for all tangible objects...even if very fine. So we adjust.

How do we know if the azimuth is off by a fraction of a degree in the way the stylus is mounted to the cantilever? We either listen and adjust or measure and adjust. How is zenith different? Never mind the debate over tracing distortion 'value' versus other parameters...

When manually aligning a cart ( to lofgren etc ) we are setting 'macro zenith'...just hoping to use a bigger visual cue ( cantilever ). The better our magnification and light the more we can attempt to use the stylus for this. Having a microscope analysis of the zenith is imo a helpful bit of info.

 

[bazelio]

A better method is needed for zenith. AM provided a roundabout method for measuring zenith distortion, and the next version will have a direct method. Zenith is next to impossible to nail visually, regardless of stylus cantilever precision. And it's such an influential parameter on the sound.

 

[ianm0]

A better method is needed for zenith. AM provided a roundabout method for measuring zenith distortion, and the next version will have a direct method. Zenith is next to impossible to nail visually, regardless of stylus cantilever precision. And it's such an influential parameter on the sound.

The day that AI can take over should not be too far away: we will then get perfect coils alignment, stylus mounting on cantilever, and precise attachment of the latter to the body. Audio Technica, Ortofon, .. should have the resources to go that way. Maybe already.

 

[J.R. Boisclair]

Here’s something to bust your brain with:

SRA is only sensitive to horizontal groove modulation and VTA is sensitive only to vertical modulation. We want both to be optimized but we can’t change one without impacting the other. The question then becomes how to weight both against each other and assess for relative importance. There is an answer to this question. We know how to model the problem in our engineering software packages and will do so as soon as our current study is completed. The study will be submitted to JAES just as our current study will be.

Similar study is to be done on the cutting side, taking into account effects of lacquer spring back. Cutting SRA doesn’t mean resultant effective lacquer groove exhibits same SRA. This is why cutting SRA and ideal playback SRA can be different.

in any case, SRA/VTA are parameters much more forgiving to being wrong at playback than zenith error and azimuth. Thank God for that since the torque tube (cantilever) on European and American cutter heads are typically ~5 degrees in variance from one another.

This much is certain: There is ONE “right” setting for your playback azimuth and zenith error correction. We know what those are. There is an acceptable range for “right” on SRA and VTA. We’ll have that answer soon.

Multivariate tests (think test records) are SO fraught with problems. I can only recommend a multivariate test for azimuth (since no other option exists) - and then only with great caution as our analysis of the quality of 9 test records revealed the problems with them for this test. Those problems started with the cutting stylus selected but didn’t end there. We are now analyzing cutting styli as well and offering the best cut of them for the recording process. Many of them are cut in a manner that causes crosstalk to be cut right into the lacquer.

At my seminars at AXPONA I emphasized that the loose tolerances in this industry on the cutting AND playback side are not a cause for despair. If we can get so much enjoyment from the grooves while being as far off as most of us (and our records) are from ideal right now then we have great reason to be OPTIMISTIC since there is so much more to get from the grooves once we attend to our alignment with care.

the results speak for themselves

 

[DetroitVinylRob]

Perhaps we are coming to a point where high-end phonograph cartridges could be vetted and sold, priced by their level of dimensional precision?!

 

[bazelio]

Perhaps we are coming to a point where high-end phonograph cartridges could be vetted and sold, priced by their level of dimensional precision?!

I assume that's already happening. If you're using Namiki, for example, the only way to achieve precision in your high end product is to either throw a lot of them away or relegate the less-precisely-assembled samples to lower end (lower priced) products in your line.

 

[J.R. Boisclair]

I assume that's already happening. If you're using Namiki, for example, the only way to achieve precision in your high end product is to either throw a lot of them away or relegate the less-precisely-assembled samples to lower end (lower priced) products in your line.

...or sold to other cartridge manufacturers! From what I've seen, I've reason to believe this may be the case.

In any case, none of them measure zenith error directly. They only look at the orthogonal relationship of the stylus shank sides relative to the cantilever. However, MANY styli do not have an orthogonal relationship between the stylus shank sides and the contact edges. You would think they should/would, but they often do not. So, you could have a stylus that erred clockwise relative to the cantilever when you assess the stylus shank sides but that same stylus can err counterclockwise when you assess the angular relationship between the contact edge and the cantilever. The latter is the ONLY thing that matters, but imaging and measuring it is a bitch.

I believe this lack of faceting orthogonality may be because the Ogura and Namiki styli have to be fitted multiple times to various jigs in order to achieve the complex faceting they have. Every time you refit the stylus to another jig you stack your tolerance errors. The simple cut of the replicant design avoids this (but creates other concerns).

 

[bazelio]

Why wouldn't other cartridge manufacturers just buy directly from Namiki?

I wouldn't say "none" measure it. I know at least one that certainly does. And anecdotally, another whose top of the line cart has measured dead nuts on with three different random samples sourced from different distributors. A coincidence maybe, but pretty unlikely.

This lack of faceting orthogonality isn't something I've ever considered before. It adds yet another variable and another reason that visual siting with lines doesn't cut it.

 

[J.R. Boisclair]

Why wouldn't other cartridge manufacturers just buy directly from Namiki?

I wouldn't say "none" measure it. I know at least one that certainly does. And anecdotally, another whose top of the line cart has measured dead nuts on with three different random samples sourced from different distributors. A coincidence maybe, but pretty unlikely.

This lack of faceting orthogonality isn't something I've ever considered before. It adds yet another variable and another reason that visual siting with lines doesn't cut it.

It is my understanding that the stylus/cantilever assembly manufacturers are struggling to meet demand and are giving priority to larger and/or longer term clients. One or more of those cartridge manufacturers are then vetting their lot and selling off their undesirables to smaller manufacturers. I am only inferring that based upon what I measure and based upon a comment made to me by a cartridge manufacturer of that practice being a reality.

I have analyzed 30 brands of cartridges by now (#31 is on the bench right now) and evidence that any of them measure zenith error directly has not manifested itself with the possible exception of the very top-end Ortofons and SoundSmiths - both of which are made easier to measure by virtue of the replicant stylus itself.

Which manufacturer are you referring to, bazelio? Also, by what means has such measuring certainty been accomplished?

 

[bazelio]

J.R., I don't want to speak for the methods employed by cartridge companies, but you named one of them. The anecdotal evidence I shared was with regards to the Opus 1 from Airtight. Myself and two others have noted that any visual deviation from parallel on the alignment grid resulted in worse measured distortion with AM. (PS: I know you're an AM detractor and I don't want to go down that rabbit hole again.). I haven't observed this with other carts. And those of us who performed these experiments have noted, that in the case of zenith, worse measured distortion always correlates to worse sound. I have made AM zenith alignment part of my routine, whereas with other parameters, I use both my ears and the tools to arrive at "the best" result.

EDIT: To be totally accurate, I don't really use the ear test on azimuth anymore either. I aim for lowest measured crosstalk.

 

[J.R. Boisclair]

J.R., I don't want to speak for the methods employed by cartridge companies, but you named one of them. The anecdotal evidence I shared was with regards to the Opus 1 from Airtight. Myself and two others have noted that any visual deviation from parallel on the alignment grid resulted in worse measured distortion with AM. (PS: I know you're an AM detractor and I don't want to go down that rabbit hole again.). I haven't observed this with other carts. And those of us who performed these experiments have noted, that in the case of zenith, worse measured distortion always correlates to worse sound. I have made AM zenith alignment part of my routine, whereas with other parameters, I use both my ears and the tools to arrive at "the best" result.

EDIT: To be totally accurate, I don't really use the ear test on azimuth anymore either. I aim for lowest measured crosstalk.

I have analyzed two of those. One went back to factory for excessive zenith error (beyond the Ogura tolerance of +/- 5 degrees). The other made it within "tolerance". I don't blame any one manufacturer specifically. They all have the same issues: namely, they don't measure zenith error, that one included based upon my two experiences with it.

See attached example of non-orthogonal stylus. Note the contact line in the center of the stylus errs counterclockwise when the stylus shank errs clockwise. That is a 8.5 degree variance from orthogonality!

 

[Solypsa]

@J.R. Boisclair Will you be selling 'blueprinted' cantilever-stylus assemblies to manufacturers?

 

[J.R. Boisclair]

@J.R. Boisclair Will you be selling 'blueprinted' cantilever-stylus assemblies to manufacturers?

Sorry, I don't understand the question.

I have been analyzing cutting styli and am just about to order a new batch of them. I see problems there too with the cuts being such that crosstalk is being cut into the grooves by virtue of the facets being asymmetric.

I know all of this may sound as a reason for despair, but that isn't how I see it. With as fantastic as our records sound right now, I love knowing that we can get MORE from them if we attend to the mechanical alignment of styli at the cutting and at playback.

 

[bazelio]

See attached example of non-orthogonal stylus. Note the contact line in the center of the stylus errs counterclockwise when the stylus shank errs clockwise. That is a 8.5 degree variance from orthogonality!

JR, how can you be sure there is absolutely zero parallax error here? I don't think it's possible. The camera requires perfect perpendicularity and centered orientation to the device under test/observation, and in this case it's really the stylus tip, in order to draw lines, measure angles, and conclude. I think this method introduces errors of its own which probably can't be quantified and will have sample over sample variation.

 

[J.R. Boisclair]

JR, how can you be sure there is absolutely zero parallax error here? I don't think it's possible. The camera requires perfect perpendicularity and centered orientation to the device under test/observation, and in this case it's really the stylus tip, in order to draw lines, measure angles, and conclude. I think this method introduces errors of its own which probably can't be quantified and will have sample over sample variation.

You are correct, there are opportunities for optical distortion all over the place! This is why I don't use the stacked photos for my documented measurements (example photo is the one I posted just above). I only use them for sharing with public so they can see the issues. The image stacking itself creates some error.

My measurement process is the result of a long, painful and expensive road I went down to find optical measurement precision. My accuracy has most certainly improved over time with much practice and the development of some rather complex customized jigs affixed to the stage that offer the opportunity to rotate the entire cartridge with the center of rotation being RIGHT AT the stylus tip.

I certainly can't take all of the credit, though. In the early days of my analysis work I hired a consultant from Leica who has a PhD in materials science to train me. Also, one of the three engineers on our research team is a Stanford PhD with decades in a career concentrating in optics. He has helped me take the accuracy to new levels.

So, while I can never be 100% certain there is zero parallax error, I know I can reduce the risk to negligible levels. In retrospect on my early work, I did make some errors that I would not make today.

 

[bazelio]

Ok to what can you reduce the error interval and how can it be verified? And if we simply accept the given error interval, then to what does it translate to in terms of margin when stating something like "3.5 degrees"?

 

[J.R. Boisclair]

Ok to what can you reduce the error interval and how can it be verified? And if we simply accept the given error interval, then to what does it translate to in terms of margin when stating something like "3.5 degrees"?

Getting the contact edge to be orthogonal to the lens is actually pretty easy. That is verified using two methods but just one of them is quite good enough. However, it took me almost a year and professional affirmation to figure that approach out!

Once I've confirmed orthogonality with the contact edge I take multiple measurements using slightly different conditions in illumination conditions (of which there are at least five variables right there), focal point and magnification. If all my measurements are within 0.25 degrees of each other, I'm doing well. I'll accept 0.33 degrees variation on Ogura or Namiki, but not replicants - in which case I can really hone it in better than that. I'm generous with my standard deviation stats, so again that is typically 0.33 degrees at worst.

 

[bazelio]

I mean... The lens surface obviously has a curvature. Job one would would be identifying top dead center and perpendicularity after that to a non-flat surface. In any event, I was sort of curious about the error margins and verification method thereof. But it's OK. Thanks.

 

[J.R. Boisclair]

I mean... The lens surface obviously has a curvature. Job one would would be identifying top dead center and perpendicularity after that to a non-flat surface. In any event, I was sort of curious about the error margins and verification method thereof. But it's OK. Thanks.

Your questions are well placed. Cheers.

 

[mtemur]

additional to parallax and optical errors there are also lots of variations mentioned above on measuring angle on a picture taken by a microscope. and still an important problem remains unsolved which is trying to measure a dynamic system with static methods.

on the other hand aligning zenith angle with AM and test record is a dynamic method for a dynamic system. I used AM and test records to setup lots of turntables and cartridges. zenith, SRA and anti-skating adjustments end up at the same alignments using both AM test record and Analogue Productions test record. if you can make record sit perfectly flat on the platter (vacuum hold down) than azimuth tracks give the same alignment too. track locations are totally different on those two records and they're cut at different lathes but software leads you to the same cartridge alignment position in the headshell. which means both records are carefully and rightfully cut and pressed. more importantly it means the alignments you make are correct and also sounds better compared to optical alignment methods.