The importance of VTA, SRA and Azimuth - pics

Lagonda said:

The only one i heard about using this measure to set VTA is Fremer, he wrote a couple of pieces on it in Stereophile, maybe his motor skills are better than his ears these days.

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Credit for developing the measuring technique and using a digital microscope goes to Wally Malewicz. Wally was a true engineer and creative thinker though not a business or marketing person. And he loved vinyl playback. He applied his skill in an effort to make some sense of the task of orienting a tiny three dimensional object in space (a stylus) so it could drive a tiny little motor (magnet and coils) to generate a tiny electrical signal that when amplified brought the New York Philharmonic into your living room.

ddk said:

A simple question for those who advocate SRA/VTA setup by numbers and IMO somewhat questionable methodology, how do you know your numbers are any good without listening? What's your baseline if you don't know what to listen for?

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Of course. The only real, a posterior, baseline is the sound of live acoustic music. Otherwise what comes out of from your stereo can sound like anything you like. If you have a baseline you can adjust by ear.

Adjusting by ear, adjusting for something presumes you know what you are adjusting for. Otherwise you are adjusting for pleasure - or whatever it is that trips your trigger - a sound in your head - your ideal sound. The notion of using measurements tries to make the adjusting less subjective, saying something like if you follow this measurement protocol you are more likely to attain output resembling input, regardless of what you think the output should be. It's an attempt to overcome the subjective for those unsure about a baseline.

Two different worlds, two different ways.

ack said:

get the industry's attention and fix the quality problems

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Err, yeah, that's the ticket! But not everyone has them.

ack said:

I will agree again that THE RIGHT measurements if DONE RIGHT - assuming one has the chops to do them - is a the correct way to START this journey, while listening is another critical part as well. But, extremely few of us have that ability to properly measure, which then leaves us with just listening as the only guiding light.

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My edit.

A correct way. I see nothing inherently contradictory in having two ways, two methods. Why is it not possible to get the same or desired result from either or both?

Aside from audiophiles liking to bicker ....

tima said:

Of course. The only real, a posterior, baseline is the sound of live acoustic music. Otherwise what comes out of from your stereo can sound like anything you like. If you have a baseline you can adjust by ear.

Adjusting by ear, adjusting for something presumes you know what you are adjusting for. Otherwise you are adjusting for pleasure - or whatever it is that trips your trigger - a sound in your head - your ideal sound. The notion of using measurements tries to make the adjusting less subjective, saying something like if you follow this measurement protocol you are more likely to attain output resembling input, regardless of what you think the output should be. It's an attempt to overcome the subjective for those unsure about a baseline.

Two different worlds, two different ways.

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It isn't that complex Tim and the only context needed is one's system and the recording, you can't set up VTA based on live music or anything outside of the system's competence. For everything else people need to educate themselves, at least a little bit to complete a task why not for this? Otherwise they can hire someone to do the job. Literally you select a couple of recordings that you know well and cover the entire the frequency range, start with the tonearm level and move the back up or down until you hear the most balanced/correct sound from the system. You should be able to hear very small changes in VTA and if you don't after raising/lowering the arm even an inch or more then it doesn't matter you're, VTA isn't going to make a difference in that system and there are more important issues to look at first.

I'm not against measurements just stating that aside from luck there's no other valid method for optimizing VTA/SRA besides listening. When there are no nominal values or industry standards and the parameters are always defined by unknown variables what are you measuring for?

david

Here is a link to the original paper by Risch and Maier from 1981 cited by Michael Fremer (article begins on page 21): https://worldradiohistory.com/Archive-All-Audio/Archive-Audio/80s/Audio-1981-03.pdf

Take home quote from the conclusion (bold is mine):

Thus, our investigations clearly show SRA more important variable than VTA. Our dialogue with cutting engineers indicates that VTA currently varies between 16 and 22 degrees, depending on the lathe system. SRA, however, is generally 91 to 95 degrees relative to the record surface in order to facilitate lacquer "chip" (cutaway strand) removal. Proper hi-fi set-up should therefore concentrate on cartridge adjustment that has the tip of the stylus pointed "back" toward the tonearm pivot, and the top of the stylus tipped "forward" so that the contact SRA face is 92 degrees between the stylus and the record surface. Such alignment will at least approximate correct SRA. (One cautionary note: True Shibata styli do not have their stylus contact area or footprint lined up with the bulk of the stylus chip, and this should' be taken into account when adjusting for proper SRA.) The effects are clearly audible on a fine audio system.

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I read this to mean that the 92 degree SRA is not the end point for set up, rather it represents a starting point for those who feel comfortable/desire to measure before fine tuning by ear.

Thank you Jazdoc. Doesn’t a level head shell more or less mean that SRA will be somewhere in the range of 91 to 95°? And if that’s the case why not just set that as a starting point and then adjust from there up or down as was previously suggested by DDK?

Listening for a “balanced” sound seems like pretty straightforward and sensible advice.

ddk said:

It isn't that complex Tim and the only context needed is one's system and the recording, you can't set up VTA based on live music or anything outside of the system's competence. ... Literally you select a couple of recordings that you know well and cover the entire the frequency range, start with the tonearm level and move the back up or down until you hear the most balanced/correct sound from the system.

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At first I thought you were just making it hard for me to agree with you, but if you really think the only context one needs to adjust a cartridge is one's system and a couple records, then we really do disagree. How do you know - as you move the tonearm up and down - what you hear is "the most balanced/correct sound"? Where does that come from David if the only context you have to gauge what sounds right is your system and a couple records? Within that context you can never get it wrong. Of course one can hear differences as you move the tonearm up and down. You can leave the tonearm in any position you want and who's to say that's not right? Do you learn what counts as balanced and correct from listening to another stereo system or the radio? Is it simply whatever you say it is at the moment? There are some who say that but I don't think so.

WBF software apparently doesn't let you quote a quote and put it in a qoute box. So I'll take JazDoc's quote and do that manually:

Risch and Maier: Proper hi-fi set-up should therefore concentrate on cartridge adjustment that has the tip of the stylus pointed "back" toward the tonearm pivot, and the top of the stylus tipped "forward" so that the contact SRA face is 92 degrees between the stylus and the record surface. Such alignment will at least approximate correct SRA.

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This is the first time I've read someone actually say which direction (out of an arc of 180) is 92-degrees. It lies on the left side of 90.

PeterA said:

Doesn’t a level head shell more or less mean that SRA will be somewhere in the range of 91 to 95°?

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I think what we're being told by folks such as J.R., who've measured a lot of cartridges, is that quality sufficient to make your statement true cannot be assumed. Maybe Ortofon (and Soundsmith?) is an exception, some here say they're generally spot-on.

If cartridge makers held themselves to a standard that a level headshell meant a 90° stylus - straight up and down - then one would think it simple to achieve 92° and adjust by ear from there. Ideally tonearm makers would say how many millimeters it takes to move the tonearm 1-degree of arc - although that's relatively straightforward to calculate - or actually put lines on their arm posts that showed this!

tima said:

At first I thought you were just making it hard for me to agree with you, but if you really think the only context one needs to adjust a cartridge is one's system and a couple records, then we really do disagree. How do you know - as you move the tonearm up and down - what you hear is "the most balanced/correct sound"? Where does that come from David if the only context you have to gauge what sounds right is your system and a couple records? Within that context you can never get it wrong.

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This isn't an argument against live music as the ultimate reference, it's a different subject and understanding balanced/correct/natural sound is a given to get anything to do with system setup right, it's up to the individual to learn. As far as setting SRA/VTA goes you can only go by what you hear from the system not by what's not there. That's what I meant by system's context.

tima said:

Of course one can hear differences as you move the tonearm up and down.

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Not necessarily. Plenty of systems out there that you would hardly hear a difference or not enough difference raising and lowering the tonearm through it's entire range. They're more common that not, all you need is a couple of audiophile power cords and few footers to flatline a system.

tima said:

You can leave the tonearm in any position you want and who's to say that's not right?

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Like everything else anyone who can do it better ! But in practice that’s all it is.

tima said:

Do you learn what counts as balanced and correct from listening to another stereo system or the radio? Is it simply whatever you say it is at the moment? There are some who say that but I don't think so.

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Already mentioned that some degree of knowledge and skill is needed to get this task done properly, up to the individual how he get's educated. My point was that currently there's no real way to accurately set VTA by some type of measuring device. @J.R. Boisclair said he's working on some type of a jig to help with VTA/SRA setting which is great but that setting still needs to be verified by ear!

david

ddk said:

that setting still needs to be verified by ear!

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Of course - otherwise, what's the point. Thanks for the follow-up.

tima said:

I think what we're being told by folks such as J.R., who've measured a lot of cartridges, is that quality sufficient to make your statement true cannot be assumed. Maybe Ortofon (and Soundsmith?) is an exception, some here say they're generally spot-on.

If cartridge makers held themselves to a standard that a level headshell meant a 90° stylus - straight up and down - then one would think it simple to achieve 92° and adjust by ear from there. Ideally tonearm makers would say how many millimeters it takes to move the tonearm 1-degree of arc - although that's relatively straightforward to calculate - or actually put lines on their arm posts that showed this!

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Hi Tim, when I wrote that I thought a level headshell would mean that the stylus rake angle was more or less in the 91-95 degree range, that covers a lot of variance, perhaps 4-6 degrees. If 1 degree is roughly 4mm in arm height for a 9" arm, that is about 20mm or slightly less than an inch, or say 3/8" either up or down, of arm height travel. If the stylus is off by more than that, perhaps something is wrong with that sample.

I would think most cartridges that we are discussing in these pages and the ones that JR is measuring should fall within that range. Perhaps JR could tell us if that is not the case. I do agree that a tighter standard would be wonderful and make life easier. I think SME designed their fixed headshells with mounting holes instead of slots because they assumed that the industry would adopt a 9,5mm hole to stylus distance which never happened.

PeterA said:

Hi Tim, when I wrote that I thought a level headshell would mean that the stylus rake angle was more or less in the 91-95 degree range, that covers a lot of variance, perhaps 4-6 degrees. If 1 degree is roughly 4mm in arm height for a 9" arm, that is about 20mm or slightly less than an inch, or say 3/8" either up or down, of arm height travel. If the stylus is off by more than that, perhaps something is wrong with that sample.

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Yes, I can accept that.

What creates curiousity is simply not knowing how close are cartridges to what the manufacturer accepts as nominal, and how far from "perfect" the manufacturer tolerates. The aftermarket in tools (Analog Majik, Feickert, Wally, etc.) appears to be ascending. JR Boisclair offers to document the physical state of a cartridge you send him and make suggestions on how to optimize its performance. How much of that curiosity is based on uncertainty how much comes from people just wanting the best setup they can achieve I don't know, but as cartridge prices go higher with new or exotic models, expectations rise with them.

The amount of time people will spend on cartridges seems, at least anecdotally, on the rise. Granted it is and always has been part of the hobby and granted people should seek knowledge and skill for themselves, yet I cannot help think this state of affairs is something of a liability for the long term viability of analog - and for the manufacturer, the viabiliy of their business efforts. Manufacturers can set themselves apart with superior build quality and consistent adherence to specs. The "magic" of small quantity hand-crafted works of art can only carry things so far. </rant>

tima said:

Yes, I can accept that.

What creates curiousity is simply not knowing how close are cartridges to what the manufacturer accepts as nominal, and how far from "perfect" the manufacturer tolerates. The aftermarket in tools (Analog Majik, Feickert, Wally, etc.) appears to be ascending. JR Boisclair offers to document the physical state of a cartridge you send him and make suggestions on how to optimize its performance.

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There are two separate categories of tools, one group like Wally's tools, protractors, scales, etc. are the ones we use to physically set up the cartridge and arm. The other category are measuring tools to verify the setup.

tima said:

How much of that curiosity is based on uncertainty how much comes from people just wanting the best setup they can achieve I don't know, but as cartridge prices go higher with new or exotic models, expectations rise with them.

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None of these are new, alignment protractors and jigs were available since the dawn of LP and we've had test records, scopes and even measuring machines like the Ortofon and AT cartridge analyzers for decades but somehow they've become indispensable mythical beasts today for some when they've been around for decades and most people didn't really need them!

tima said:

The amount of time people will spend on cartridges seems, at least anecdotally, on the rise. Granted it is and always has been part of the hobby and granted people should seek knowledge and skill for themselves, yet I cannot help think this state of affairs is something of a liability for the long term viability of analog - and for the manufacturer, the viabiliy of their business efforts. Manufacturers can set themselves apart with superior build quality and consistent adherence to specs. The "magic" of small quantity hand-crafted works of art can only carry things so far. </rant>

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I believe that most of this is caused by lack of or misguided education by those who benefit from creating fog and mystery surrounding this matter and sometimes even by blind leading the blind. Nothing has changed in the last 60-70 years of turntables set up of tonearm and cartridges on standalone players is still the same process it’s always been. Mount the cartridge in the headshell, align the tonearm with a protractor, set the tracking force with a scale and if the tonearm has the option raise or lower the it to where it sounds best. Doesn't have to be perfect at first attempt either, you can change the VTA if you find something missing or off in a week or two or anytime you wish. One can spend a millions dollars on setup tools and whatnots and it won’t change the basic process, always the same 3-4 steps as it's always been. People should just get to it and try for themselves, nothing will happen if they don't get it right at first attempt!

david

Wow, I walked away and this conversation took off. I didn't get any emails advising any activity was going on and just happened to drop in today to refer to something and noticed you guys having a RESPECTFUL conversation which makes it easy for me to re-engage. THANK YOU!

Some quick points are all I have time for:
1. Absolutely True: analog alignment principles that were established decades ago are still the ONLY and best way to ensure proper static and dynamic relationships between the groove and the equipment meant to mechanically extract the information from those grooves.
2. WallyTools contributions have not been original, they have only offered the tools and methodology to maximize the accuracy of the setup given what has long been known about the geometry and physics of analog playback. The "new record collection" arcs on the WallyTractor are still Leofgren and Baerwald formulas, but have been "updated" based upon the increasing innermost groove radius on records produced after 1990.
3. Conical and elliptical stylus profiles will NOT benefit nearly as much from fine attention to setup parameters. Fine minor radius stylii DEMAND fine attention to setup.
4. I agree that Michael's approach to measuring SRA with a USB microscope as taught to him by Wally carries some risks to accuracy which is exactly why I am developing the WallySRA. I have scrapped the original design which was a vice-like jig that the cartridge is mounted into as I could not repeatedly get at least 0.05mm tolerance on cartridge height. I am moving to another type of jig. However, the WallyZenith has my attention right now as at least 60% of the cartridges I analyze have a zenith error of greater than 1%. When aligned correctly, the sonic results are not subtle. Look for more on this from Fremer.
5. I continue to encourage use of Fremer's method of measuring SRA but with some further suggestions. First, make life easy on yourself and CONTROL the XYZ axes. Get a XY stage like this: https://www.supereyes-store.com/col...and-for-digital-microscope-endoscope-otoscope to put your Z axis microscope holder on. A Z axis holder looks like this: https://www.dinolite.us/en/products/accessories/dino-lite-stands/ms34b-r2. Just make sure you get one where you can rotate the collar that holds the scope by 90 degrees - I'm not SURE this one offers that ability but I know others do. Here is one for the otoscope style scopes (which have an advantage in their small diameter) which definitely does offer a rotation: https://www.supereyes-store.com/collections/new/products/z009-fine-focus-stand
6. BE SURE to have the stylus as close as possible to the edge of the platform it is resting upon so that the platform edge can be in focus and used as a reference against which the stylus angles are drawn.
7. Shibata and SoundSmith "Optimized" Line Contact stylii cannot be determined for SRA using the same calculation as the contact edges are NOT parallel to the shank. You need about 400x magnification to see the contact edge on these profiles and you need to get the illumination right.
8. It is best to have a contrasting color behind your stylus. A white piece of paper will do. Keep it close as possible to the stylus. Cut a very narrow strip of paper 2" long and 1-2mm wide. Bend it and it will lay on edge. Move it into position behind the stylus. Use your white balance function on your camera software to get the colors and contrast popping. Try illuminating from the back or back-side.
9. Make sure the stylus platform is at record height and, dear God, please make sure you have your VTF dialed in and your anti-skate OFF. SELF PROMOTION WARNING à la MISTER T.: I pity the fool who don't use a WallySkater and has no idea their tonearm has internal horizontal forces pushing the cantilever!
10. Understand the importance of perpendicularity between cantilever and camera. Study this drawing: https://www.analogplanet.com/content/another-angle-digital-can-worms. Without the WallySRA I do not have a solution for you on this one other than "do your best".
11. Whether recording engineers realize or not, cutterheads at obtuse angles greater than 90 degrees (which they MUST be to avoid crushing the chip back onto the lacquer surface) are subject to downward vector forces. I go into this in WallySchool! Blog. Such vector forces get stronger the greater the angle increases past 90 degrees. The vector forces FIGHT the lathe motor and cause a loss of efficiency. Loss of efficiency means what the cutterhead is being asked to carve into the lacquer won't be exactly what it cuts. Read: distortion. We have to trust our engineers to get this right but we can safely assume some records will be cut at 91 and some at 93 and so on. I am not a proponent of adjusting all the time for every record - even for record thickness. Let's get our angles as accurate as possible and then simply enjoy the music and not obsess.
12. The maximum difference between the thinnest and thickest record is 1.2mm. For a 9" tonearm, that is about a 0.3 degrees variation in SRA. Less for longer arms. In my experience, this figure is at the limit of perceptibility and I don't worry about it. Besides, most of my records aren't the "thinnest" and most of them aren't the "thickest" but are somewhere in between. As Wally would say, "FINE!! Now enjoy analog."
13. Changing tonearm height also changes azimuth. There is no escaping this except on non-pivoted linear tonearms. If you insist on setting SRA by ear, you will need to change azimuth with your tonearm height changes. Use this calculator for that sisyphean effort: https://www.wallyanalog.com/sra-impact-to-azimuth-calculator. You will also need to adjust your VTF with tonearm height changes since most tonearms are not neutral balanced. Wally calculated that on the Kuzma 4Point tonearm, if you have a cartridge with 35µm/mN compliance, tonearm height changes will NOT IMPACT SRA AT ALL! Granted, 35µm/mN is very compliant, but you get the idea.
14. I have mentioned that I am NOT a fan of multivariate testing as it is more difficult, doesn't reveal construction flaws and, by definition, doesn't allow you to measure the parameter of interest DIRECTLY. However, if you can be assured that the other parameters ARE setup perfectly, then you remove the latter concern in ONE setup parameter only. I'm going to stay mum on what this parameter is for now until I can give you the solution. I am still putting this hypothesis through its paces. Sorry for the tease - but not really. ;-)
15. To Tima at #210. Your photo is taken too high relative to the stylus platform. Get that camera down so that the platform edge is taking up the bottom 1/3 to 1/2 of the photo frame and you see very, very little to none of the top surface of the platform. You can use the edge of the platform as a more reliable level reference for your angle measurements. Do this and your SRA reading will change.
16. I have the luxury of hearing many very high end cartridges due to my analysis work. With the shims I make for each one that compensate for SRA and azimuth, I can quickly listen to what the cartridge sounds like at ideal SRA/azimuth/zenith and at level headshell reference. However, without knowing where "perfect" alignment for a given cartridge is many audiophiles go about their analysis by ear. We tend to stop ourselves when the tonearm looks like it is tilted too much one way or the other, not believing "ideal" could be so far off. When we remain less than enthused with the results, either we declare the cartridge unworthy or we look to compensate for the sonic issues elsewhere in the system. Imagine if our native SRA is 96 degrees and, starting from a level headshell, we lower the arm until it can't go down any further. Let's say that SRA value is now 94.5 degrees. We can see the tonearm is visibly tilted and declare that this is as good as it gets. We listen and feel that things are still a bit bright sounding and the bass isn't as full as it could be so we begin treating reflection spots in the room and moving the speakers around to gain a bass boost. I think we have ALL done this unknowingly at some time or another in our analog efforts - compensate for an inadequate analog setup with systemic changes. So, I tell my customers that once their cartridge is setup to angular perfection and they are unsatisfied that they are likely to have systemic issues that the new alignment has revealed. This is a warning I give them, but no one so far has reported back anything other than being pleasantly surprised by the improvements angular perfection offers.
17. I have attached my most recent cartridge analysis report. As you can see, this cartridge should be returned to the manufacturer for repair or replacement. I have redacted the owner's name and the name of the cartridge as I do not wish to make enemies by publicly "outing" them. This cartridge costs $7,000. There is NO WAY any tonearm could adjust for the stylus mount error in SRA and, unless you have one of my prototype WallyZeniths, there is no way to compensate for the zenith error. I have made a custom shim for this cartridge with very high-density material and have listened to it "corrected" on all parameters and it does sound great, but no one should have to go through this to get the most out of the cartridge!

I hope that helps. So much for my "quick points"!

tima said:

I came to the conclusion that what is missing is a means to hold the small microscope firmly and to adjust it by very small amounts in three-dimensions. If the stand to do that is out there I'd like to know what it is. The slightest movement will move the scope in an unhelpful way.

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I have the perfect tool for what you're asking for:


Dino-lite makes a stand that firmly holds the microscope and provides finely adjustable control in the 3 dimensions you're looking for. You'll need to get the RK-10 , the RK-10-PX, and one other part (which escapes me now) to hold the microscope so that it's pointing horizontally.

I purchased all of them about 6 months ago. They are exactly what you need.

I just quickly snapped the following picture....

J.R. Thanks for the detailed exposition. I do have a question to raise with regard to Fremer's method of measuring SRA using a CD as the platform. A CD has much finer grooves vs a record. When a stylus rests on either CD or LP, the point(s) of the stylus in contact with the grooves in each is different. Consequently SRA measured will be different. My question is how different? Will it or will it not be significant enough?

ianm0 said:

J.R. Thanks for the detailed exposition. I do have a question to raise with regard to Fremer's method of measuring SRA using a CD as the platform. A CD has much finer grooves vs a record. When a stylus rests on either CD or LP, the point(s) of the stylus in contact with the grooves in each is different. Consequently SRA measured will be different. My question is how different? Will it or will it not be significant enough?

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RIAA minimum standard stereophonic groove width is 25 microns. No standard for maximum but they do get up to 80 microns. Let's assume 60 micron width. since the cutter head cuts a 90 degree cross-sectional groove profile, the depth will be 52 microns. This means the deepest part of the groove is 52 microns below the surface of the record. The stylus won't reach all the way down to the bottom, but for this case let's assume maximum impact scenario: it reaches groove bottom. The pivot point of this difference in SRA (surface of record vs. down in the groove) is the tonearm pivot point, NOT the cantilever pivot point. Assuming a 9" tonearm then, the difference in SRA between the two stylus locations is 0.0021 degrees. SOMEWHERE out there is an audiophile who claims to hear that difference. ;-)

By way of contrast, changes of 52 microns at the cantilever pivot point assuming a 5.5mm effective length result in a 0.58 degree SRA change. Of course, this cannot happen during playback without shooting the stylus clear out of the groove (see above for the minimum RIAA groove width standard) but I think a good case could be made that the stylus can change SRA during playback of approximately +-0.12 degrees at VERY rare moments of maximum vertical modulation. Zenith can make the same shifts during maximum horizontal modulation.

squasher said:

I have the perfect tool for what you're asking for:

Dino-Lite Digital Microscope

Dino-lite makes a stand that firmly holds the microscope and provides finely adjustable control in the 3 dimensions you're looking for. You'll need to get the RK-10 , the RK-10-PX, and one other part (which escapes me now) to hold the microscope so that it's pointing horizontally.

I purchased all of them about 6 months ago. They are exactly what you need.

I just quickly snapped the following picture....

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Yes it gave me the basis to achieve a starting point --with final evaluation by ear of course the Dino-lites are easy to use.
Remember to remove the front plastic nose cone if you want to get real up close.
BruceD

J.R. Boisclair said:

. Assuming a 9" tonearm then, the difference in SRA between the two stylus locations is 0.0021 degrees. SOMEWHERE out there is an audiophile who claims to hear that difference. ;-)

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This estimate is probably correct. But this brings out the doubt on the validity of another common belief: raising a 9" tonearm by 4 mm results in a change in SRA of 1 deg. This is true if the cantilever were RIGIDLY attached to the tonearm, i.e. no flexing when the tonearm height is altered. However the cantilever does flex. We have to look at two rotations, not just the one above the tonearm pivot. If both the cantilever and the tonearm were raised the same distance, the angular changed at the cantilever is magnified due to the its short dimension ~ 10 mm vs the effective length of the tonearm ~ 240 mm. Of course, this ratio of 24 never happens in real life, and how much it is depends on cartridge compliance, stylus profile geometry, ... In real life, I believe the aforementioned angular magnification is significantly larger than 1 and invalidates the simple geometric relation between changes in tonearm height and SRA. It is cartridge dependent.

ianm0 said:

This estimate is probably correct. But this brings out the doubt on the validity of another common belief: raising a 9" tonearm by 4 mm results in a change in SRA of 1 deg. This is true if the cantilever were RIGIDLY attached to the tonearm, i.e. no flexing when the tonearm height is altered. However the cantilever does flex. We have to look at two rotations, not just the one above the tonearm pivot. If both the cantilever and the tonearm were raised the same distance, the angular changed at the cantilever is magnified due to the its short dimension ~ 10 mm vs the effective length of the tonearm ~ 240 mm. Of course, this ratio of 24 never happens in real life, and how much it is depends on cartridge compliance, stylus profile geometry, ... In real life, I believe the aforementioned angular magnification is significantly larger than 1 and invalidates the simple geometric relation between changes in tonearm height and SRA. It is cartridge dependent.

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Hello ianm0,

Everything is calculable when you have the right dimensions and compliance. For dynamic conditions you'll need the coefficient of friction as well.

You are correct that on most tonearms (those that are not neutral balanced) a change in tonearm height will also cause a change in VTF, which causes a change in SRA (it changes azimuth too, but that's another matter). The degree to which this change is effected depends upon the distance between the horizontal bearing and the center of gravity of the tonearm and the compliance of the cartridge. The 4mm height change causing a 1 degree SRA change is a good rule of thumb. Is it perfect? NO! However, if we worried about ALL the variables that are impacted on our multivariate analog transcription devices, we'd never get any time in for listening to music! At some point in engineering, you have to choose what is significant enough to worry about what determine what is "noise". If you play only conical styli - or even some elliptical styli, you'll do well to think that pretty much all I care about in analog playback is noise - and that's just fine!

The 4mm (actually, it's 4.2mm but who's counting?!) per 1 degree SRA on a 9" tonearm is useful and MOSTLY accurate. Here is some more useful information (the "Tonearm Ð Change" can be read as "Tonearm arm wand angular change":