Analog Magik

J.R. Boisclair · Jul 13, 2024

Gents, a few points that might be helpful to you:
1. The test track for "VTA" is horizontally modulated (if memory serves me correctly) which means is it not useful for measuring VTA. SRA perhaps, but not VTA since VTA is only sensitive to vertical modulations. You cannot measure both from the same track as the mechanical distortion characteristics are VERY different from each other.
2. When you raise and lower the tonearm, the dominant distortion characteristics are thrown off by vector forces, not VTA or SRA. This will be clear to you if you use wedge shims at the headshell to impact your SRA and VTA. Yes, it is not ideal to have another material between your headshell and cartridge (or, more accurately, it is not ideal to add an additional join) but not all design parameters weigh equally on our sonic experience and I think you will be surprised when you start to play with this. Most all cartridges need to get DOWN, not up, in VTA.
3. I have analyzed several hundred cartridges. The average error from ideal VTA is 9 degrees from ideal and 7 degrees from maximum acceptable (dynamically measured at level headshell at height equaling height of cartridge under nominal VTF). We know what the goals are because we know what the various cutterhead vertical modulation angles are net of lacquer springback.
4. Since SRA has NEVER been truly scientifically studied and there are several reasons why it may not weigh equally to VTA in terms of audibility - particularly at low VTF - it deserves a deep dive. Our little research team is currently designing the experiment and accumulating the necessary equipment but may not commence with it until our zenith error study has been submitted for publication.
5. There is no such thing as "zenith angle". There is "zenith error" and there is "zenith error correction", but these things do not replace "offset angle" which is what most people mean when they say "zenith". I must admit some responsibility for this as I may have carelessly used the term in that manner in the early days we were researching zenith error. Sorry about that!

BruceBW · Jul 13, 2024

Thanks J.R.... to your point 1

While I get easily repeatable results using the Analog Magik VTA test for zenith, I have never gotten consistent, repeatable results when trying to use it to adjust VTA. So what you state makes sense at least as far as my results go. I've also tried the "Fremer Method" with the USB scope looking for the perfect SRA, but I find this so subjective it is in my mind, only useful to get you somewhere close. I have resorted to getting the headshell visibly parallel with a record using one of the blocks with lines etched in it and error on the side of being a little low in the back. I don't see how one can do much better given the various thicknesses of the vinyl we play. However, always looking for a better way.

J.R. Boisclair · Jul 13, 2024

If you use a decent scope and follow my instructions on how to control your approach angles (read the WallyScope instructions), you can get very tightly controlled SRA measurements. My own error using the WallyScope is +/-0.35 degrees. Since neither SRA nor VTA are very sensitive parameters to angular change (unlike zenith error and azimuth) 0.35 degrees is nothing at all.

HOWEVER, I don't believe SRA is nearly as important as VTA for quite a number of reasons, but I can't yet prove it.

The acrylic blocks are good enough to give you a sense of comfort but the instructions conveniently do not warn that the approach is riddled with parallax error.

In any case, do not use your tonearm height adjustment to listen or measure for ideal SRA or VTA. You'll be experiencing plenty other parameters before you'll notice a change in SRA or VTA.

Calle_jr · Jul 14, 2024

J.R. Boisclair said:
The test track for "VTA" is horizontally modulated (if memory serves me correctly) which means is it not useful for measuring VTA

Agree, hence I didn't understand.
But I think lateral cut tracks can be used for VTA/SRA very effectively and more robust than measuring distorsion levels.
I compare the signal voltages for 100Hz, 1kHz and 10kHz mono tracks and raise/lower VTA if the 100Hz/10kHz voltage is greater than the 1kHz.

I totally agree with you regarding SRA. It's a separate issue and I think only a geometric relation between SRA and VTA.

mtemur · Jul 14, 2024

J.R. Boisclair said:
Gents, a few points that might be helpful to you:
1. The test track for "VTA" is horizontally modulated (if memory serves me correctly) which means is it not useful for measuring VTA. SRA perhaps, but not VTA since VTA is only sensitive to vertical modulations. You cannot measure both from the same track as the mechanical distortion characteristics are VERY different from each other.
2. When you raise and lower the tonearm, the dominant distortion characteristics are thrown off by vector forces, not VTA or SRA. This will be clear to you if you use wedge shims at the headshell to impact your SRA and VTA. Yes, it is not ideal to have another material between your headshell and cartridge (or, more accurately, it is not ideal to add an additional join) but not all design parameters weigh equally on our sonic experience and I think you will be surprised when you start to play with this. Most all cartridges need to get DOWN, not up, in VTA.
3. I have analyzed several hundred cartridges. The average error from ideal VTA is 9 degrees from ideal and 7 degrees from maximum acceptable (dynamically measured at level headshell at height equaling height of cartridge under nominal VTF). We know what the goals are because we know what the various cutterhead vertical modulation angles are net of lacquer springback.
4. Since SRA has NEVER been truly scientifically studied and there are several reasons why it may not weigh equally to VTA in terms of audibility - particularly at low VTF - it deserves a deep dive. Our little research team is currently designing the experiment and accumulating the necessary equipment but may not commence with it until our zenith error study has been submitted for publication.
5. There is no such thing as "zenith angle". There is "zenith error" and there is "zenith error correction", but these things do not replace "offset angle" which is what most people mean when they say "zenith". I must admit some responsibility for this as I may have carelessly used the term in that manner in the early days we were researching zenith error. Sorry about that!

You can never achieve perfect VTA, following the same arc that cutter head stylus rides vertically. The reason for that, cutter head cantilever or cylinder block that stylus attached to one end is significantly longer than any cantilever that can be found on a cartridge. Since cartridge cantilevers are shorter the only way to replicate cutter head’s vertical arc is to go lower on VTA than cutter head’s. Normally cutter head VTA is between approximately 15-22 degrees. It is almost impossible to go lower than 15 or 10 degrees VTA. I’m not convinced on VTA being more important than SRA cause VTA is mainly (not only) related with out-of-phase signal which is not as popular as it has been early days of stereo.

J.R. Boisclair · Jul 14, 2024

Calle_jr said:
Agree, hence I didn't understand.
But I think lateral cut tracks can be used for VTA/SRA very effectively and more robust than measuring distorsion levels.
I compare the signal voltages for 100Hz, 1kHz and 10kHz mono tracks and raise/lower VTA if the 100Hz/10kHz voltage is greater than the 1kHz.

I totally agree with you regarding SRA. It's a separate issue and I think only a geometric relation between SRA and VTA.

The mechanical distortion thrown off by VTA is only present during vertical excursion of the stylus. By “vertical“ I mean any path of travel that isn’t on the horizontal plane. As the vector approaches perfectly vertical the distortion characteristics are most present.

VTA wasn’t even an issue until the advent of stereo reproduction.

If you are using a horizontally modulated signal it certainly isn’t VTA that you’re measuring. We could be forgiven for thinking so because raising and lowering the tonearm changes the distortion reading quite a lot.
However, raising and lowering the arm changes multiple vector forces that are FAR more dominant on a degree for degree basis versus SRA or VTA. Therefore, it isn’t VTA or SRA that is being measured when we adjust arm height. We know this from the computational analysis we’ve been doing on zenith error and from practical application with our corrective shims.

By the way, when zenith error is present, it induces a vertical excursion that isn’t otherwise cut into the groove (we did an animation on this a couple years ago) so perhaps the distortion characteristics of VTA will make themselves manifest at that point but the information isn’t very helpful because it is only a second order phenomenon.

There is an animation to show the mechanical distortion characteristics of VTA in this video:

J.R. Boisclair · Jul 14, 2024

mtemur said:
You can never achieve perfect VTA, following the same arc that cutter head stylus rides vertically. The reason for that, cutter head cantilever or cylinder block that stylus attached to one end is significantly longer than any cantilever that can be found on a cartridge. Since cartridge cantilevers are shorter the only way to replicate cutter head’s vertical arc is to go lower on VTA than cutter head’s. Normally cutter head VTA is between approximately 15-22 degrees. It is almost impossible to go lower than 15 or 10 degrees VTA. I’m not convinced on VTA being more important than SRA cause VTA is mainly (not only) related with out-of-phase signal which is not as popular as it has been early days of stereo.

The distortion characteristic of VTA vs the cutterhead’s NET vertical modulation angle are not the same as the mechanical distortion characteristic of vertical modulation RADIUS vs playback tracking radius. You are certainly correct that the cutting radius in the playback radius are very different. Typical distance from stylist tip to pivot point of a cantilever assembly is about 6.25 mm. The torque tube on a cutterhead can be more than 25 mm. However, because the total arc travel is so small this mechanical distortion is likely to be very, very little. Perhaps even negligible??

Since there is nothing that can be done about this with cartridge technology today, we won’t bother studying this.

I originally thought the same as you that there isn’t enough purely vertical information in the groove to make VTA a significant parameter. However, when you do the math on hard left channel and hard right channel distortion characteristics as a result of VTA being wrong, you might change your mind. The path vector doesn’t need to be purely vertical for the distortion characteristics to ensue. 45° is plenty to get the job done. Additionally, if you look into a microscope at a stereo musical groove and you notice every time the groove gets wider and narrower (which is constantly) I think you might feel differently as well.

I haven’t done my video on SRA yet. I will begin to layout my case for why SRA may not be nearly as important as we’ve been thinking. I’ll be filming it next week. I look forward to your thoughts on it.

mtemur · Jul 14, 2024

J.R. Boisclair said:
However, because the total arc travel is so small this mechanical distortion is likely to be very, very little. Perhaps even negligible??

I don’t think it’s negligible. If it is, then differences in VTA is negligible too. Saying VTA is extremely important and difference between arcs drawn by 25mm and 6.5mm radiuses are negligible sounds pretty inconsistent.

This (25mm and 6.5mm) is the only important thing about VTA. Vertical arc drawn by stylus is the very thing that makes VTA and nothing else.

BTW just like zenith angle the term Vertical Tracking Angle (VTA) is not appropriate cause it is the cutting stylus’ arc that we want our cartridges’ cantilevers to ride the stylus on. If lengths of both cutter head cantilever (torque tube) and cartridge cantilever had been the same we may only talk about angle to replicate the same arc but they’re not. Vertical Tracking Error is more appropriate IMHO cause angle doesn’t define anything alone when there is an arc to follow.

Calle_jr · Jul 14, 2024

J.R. Boisclair said:
If you are using a horizontally modulated signal it certainly isn’t VTA that you’re measuring. We could be forgiven for thinking so because raising and lowering the tonearm changes the distortion reading quite a lot.
However, raising and lowering the arm changes multiple vector forces that are FAR more dominant on a degree for degree basis versus SRA or VTA. Therefore, it isn’t VTA or SRA that is being measured when we adjust arm height. We know this from the computational analysis we’ve been doing on zenith error and from practical application with our corrective shims.

Thanks, that makes total sense.
In this case, why not look at the waveform for a vertical cut sine and compare it to an ideal sine?

J.R. Boisclair · Jul 14, 2024

mtemur said:
I don’t think it’s negligible. If it is, then differences in VTA is negligible too. Saying VTA is extremely important and difference between arcs drawn by 25mm and 6.5mm radiuses are negligible sounds pretty inconsistent.

If you think this is negligible you’re wrong. This (25mm and 6.5mm) is the only important thing about VTA. Vertical arc drawn by stylus is the very thing that makes VTA and nothing else.

BTW just like zenith angle the term Vertical Tracking Angle (VTA) is not appropriate cause it is the cutting stylus’ arc that we want our cartridges’ cantilevers to ride the stylus on. If lengths of both cutter head cantilever (torque tube) and cartridge cantilever had been the same we may only talk about angle to replicate the same arc but they’re not. Vertical Tracking Error is more appropriate IMHO cause angle doesn’t define anything alone when there is an arc to follow.

I think we’ll have to agree to disagree.

The two elements at play here are differences in the arc of travel caused by different lengths of the cantilever versus the torque tube and secondly a vector angle caused by differences in VTA versus net VCA. The math is quite easy if you do comparisons between the two different phenomena.

Minimum groove width is 25 µm (IEC standard) and while I don’t remember there being a maximum width it is certainly limited by the thickness of the nitro cellulose layer. A typical non-modulated groove with is 50 µm (2 mils). If we assume that is the mean then if we say the deepest possible groove is 100 µm then I think we would be in the ballpark if not a good deal over. There is now enough data to do the distortion analysis on arc travel differences.

By comparison, calculate the difference in stylus velocity for a VCA at 18° and a VTA of 30° (which is very typical). You can assume a perfectly vertically modulated sine wave or a 45° or whatever you like.

I think you may see something interesting.

J.R. Boisclair · Jul 14, 2024

Calle_jr said:
Thanks, that makes total sense.
In this case, why not look at the waveform for a vertical cut sine and compare it to an ideal sine?

View attachment 133759

You are on the right path. Keep going!

BruceBW · Jul 14, 2024

J.R. Boisclair said:
You are on the right path. Keep going!

what do you mean "right path" ?

seems very simple so why just "right path" ?

can you point us to a test record that has a vertically cut sine wave to try it?

J.R. Boisclair · Jul 14, 2024

BruceBW said:
what do you mean "right path" ?

seems very simple so why just "right path" ?

can you point us to a test record that has a vertically cut sine wave to try it?

Because like most things in mechanical transcription, it isn't ever as simple as it seems. It's a multivariate environment which is why I make such a big deal about controlling for the variables.

As for test records, after spending a couple thousand dollars over the last few years looking for reliable test records, we've given up and have been in search instead for a cutterhead with KNOWN cutting angles (all four) and a known degree of error. We've started cutting our own lacquers for our our own research. You might watch our video on VTA and read the latest blog on my "analog trip" to Greece if you want to know a bit more.

Calle_jr · Jul 15, 2024

BruceBW said:
can you point us to a test record that has a vertically cut sine wave to try it?

Track B04 on Analogue Productions Ultimate Analogue Test LP has a vertically cut 1kHz sine wave.
If you (like me) use UATLP for e.g. zenith and azimuth adjustments, I figure we may as well use it for VTA adjustment.

I mean, the standard for VMA is (afaik) still 20+/-5o. Add to that the deviations in cantilever design as Boisclair mentions, plus tolerances. If we are lucky, we will be ok with a mean value adjustment of VTA.

I know the deviations even between test records are quite large. I compared UATLP, CBS STR-100, CBS STR-112, Hi-Fi News HFN-002, Ortofon Test Record and Feickert Adjust+ Test Record.
What I didn't know until recently is there are quite big differences between lacquers of the same release. Track A05 differs 3dB in level and 5µs in phase tested on the same player at the same time with the same test equipment!

BruceBW · Jul 15, 2024

J.R. Boisclair said:
As for test records, after spending a couple thousand dollars over the last few years looking for reliable test records, we've given up and have been in search instead for a cutterhead with KNOWN cutting angles (all four) and a known degree of error.

If test records are so unreliable, doesn't that mean that ALL records are unreliable? I don't disagree that it is better to be as close to the ideal as we can be, but if every record we play was cut with unreliable parameters, aren't we really chasing an ideal that doesn't exist. Why bother to get my alignment "perfect" if every record I play is so imperfect?

Seems that making my alignment a little bit this way or that will make some records sound better and some sound worse.

At some point shouldn't we just say it is close enough? I mean, my setup sounds pretty damn good to me as is.

J.R. Boisclair · Jul 15, 2024

BruceBW said:
If test records are so unreliable, doesn't that mean that ALL records are unreliable? I don't disagree that it is better to be as close to the ideal as we can be, but if every record we play was cut with unreliable parameters, aren't we really chasing an ideal that doesn't exist. Why bother to get my alignment "perfect" if every record I play is so imperfect?

Seems that making my alignment a little bit this way or that will make some records sound better and some sound worse.

At some point shouldn't we just say it is close enough? I mean, my setup sounds pretty damn good to me as is.

That is a reasonable question. The answer is STATISTICS. The mastering engineers are aiming at the same angles (with certainty for 45/45 groove symmetry with respect to perfectly vertical axis and the collinearity of L-R cutting edges with radial line of the lacquer but within known range limits for cut rake and vertical modulation angle). The degree to which they can err is equally likely in clockwise or counterclockwise direction. The result is a normal distribution curve of error.

SOOOOO...we stand in the best possible position to get the most out of all records if we aim for the MEAN.

Lagonda · Jul 15, 2024

BruceBW said:
If test records are so unreliable, doesn't that mean that ALL records are unreliable? I don't disagree that it is better to be as close to the ideal as we can be, but if every record we play was cut with unreliable parameters, aren't we really chasing an ideal that doesn't exist. Why bother to get my alignment "perfect" if every record I play is so imperfect?

Seems that making my alignment a little bit this way or that will make some records sound better and some sound worse.

At some point shouldn't we just say it is close enough? I mean, my setup sounds pretty damn good to me as is.

And all this can be easily done with your ears, if you have decent hearing. You start with a visual approximation and do the finer adjustments with your hearing. All these tools and measuring softwares are only important if you don't hear that well, and then why bother, just use digital !

BruceBW · Jul 15, 2024

Lagonda said:
And all this can be easily done with your ears, if you have decent hearing. You start with a visual approximation and do the finer adjustments with your hearing. All these tools and measuring softwares are only important if you don't hear that well, and then why bother, just use digital !

Disagree, completely

even with a variety of test equipment and jigs and software, Optimizing an alignment takes considerable time. With 3 axis of rotation and effective lengths that are all interactive the idea that you can do this by starting with just a visual approximation is a pipe dream. Why, because teeny tiny changes make big differences, once you start moving the cartridge you have no idea where you are without measuring….

Lagonda · Jul 15, 2024

BruceBW said:
Disagree, completely

even with a variety of test equipment and jigs and software, Optimizing an alignment takes considerable time. With 3 axis of rotation and effective lengths that are all interactive the idea that you can do this by starting with just a visual approximation is a pipe dream. Why, because teeny tiny changes make big differences, once you start moving the cartridge you have no idea where you are without measuring….

I never said it does not take time, but you can certainly listen and hear if things are getting better, if not you move in the other direction. Check your VTF with a good scale, everything else can be done with paper cutouts that come with your arm. You will never get more than a approximation anyway if you cant listen and recognize the best cartridge position with your ears. Everything comes to life when you are there. Measure, set and forget is just being lazy.

BruceBW · Jul 15, 2024

Lagonda said:
I never said it does not take time, but you can certainly listen and hear if things are getting better, if not you move in the other direction. Check your VTF with a good scale, everything else can be done with paper cutouts that come with your arm. You will never get more than an approximation anyway if you cant listen and recognize the best cartridge position with your ears. Everything comes to life when you are there. Measure, set and forget is just being lazy.

I never said measure set and forget.,
And you couldn’t possibly be more wrong…..
It is impossible to get zenith right with paper cutouts
It is impossible to get azimuth right with paper cutouts
It is impossible to set antiskaing with paper cutouts
We are done here, at least I am.. good luck with your methods.

Analog Magik

Well-Known Member

Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Well-Known Member

Member

Well-Known Member

Well-Known Member

Member

Well-Known Member

VIP/Donor

Member

VIP/Donor

Member

Similar threads