How to Use a USB Digital Microscope to set 92 Degree Stylus Rake Angle (SRA)

The stylus rake angle is the angle the stylus’s “contact patch” makes to the record surface. If you have a relatively inexpensive cartridge with a spherical stylus you don’t have to worry about SRA because the contact area remains the same regardless of arm height. On the other hand, elliptical styli along with the more severe “line contact,” Shibata, Geiger, Ortofon and other long, narrow contact patch “cutting edge” (poor metaphor!) stylus profiles require careful SRA setting to perform as designed.

These “severe” stylus profiles have the ability to more accurately trace the vertical modulations made by the sickle-like lacquer cutting stylus that is offset from true vertical and thus produces an angled cut, but if they are not properly aligned they bang into the vertical modulations rather than track them.

The more accurately the playback stylus replicates the cutter stylus angle, the less IM (Intermodulation Distortion) is produced, resulting in smoother yet far more detailed sound. Setting SRA by “ear” usually meant going from brighter, harder sound when set too high, to duller, thicker and less focused sound when set too low.

Once we began examining styli under the microscope it became obvious that finding the “sweet spot” was often a matter of luck and that often it would be impossible using the conventional “arm parallel to the record surface” starting position.

That’s because we found that the angle at which the stylus gets inserted into the cantilever varies widely even among samples of the same cartridge! So it’s hardly useful when a manufacturer says “start with the arm parallel to the record surface and move slightly up or down from there,” unless you can be sure the stylus has been inserted according to “spec” in the first place.

The pioneer in using digital microscopy to set SRA—at least for me— is Mr. Wally Malewicz, a Minnesota based mechanical engineer and vinyl fanatic who has been instrumental in my analog technical education over the past decade.

Why is 92 degree SRA the way to go? Please download and read this article, originally published in Audio magazine. Thanks to the Bonnier corporation’s generosity, we’ve gotten permission to offer it to you.

I believe it will convince most everyone that 92 degrees (two degrees beyond perpendicular to the record surface) is the ideal stylus rake angle. Considering that to change by one degree the SRA on a nine-inch arm requires a four millimeter height change at the pivot end, that setting should be fine regardless of record thickness.

The USB digital microscope I use is the Dino-Lite AMT313. It costs $249 and that includes MAC/PC compatible software. Dino-Lite makes numerous models and there are other companies making such devices but this is the one recommended to me. Resolution is 640x480 pixels (VGA). Magnification is continuously adjustable from between 10 to 200x.

You’ll also need to purchase a microscope stand. I use the BigCatch Accessories series MS32W Articulating desktop stand ($40), but you can find others through a web search.

The first step in using the AMT313 or whichever model you choose is to remove the clear plastic LED shield ring. Unless you remove it you cannot get close enough to the stylus to get a good picture. It’s held in place with an adhesive—probably Cyanoacrylate (AKA “Crazy Glue”).

To remove the shield, use both of your thumbs and gently put pressure on the side of the shield. Then rotate the microscope and repeat on the opposite side. You’ll need to go back and forth numerous times applying moderate pressure until nothing happens and the process begins driving you crazy! Don’t give up! Just keep doing it. Eventually the shield will pop off.

Next, install the software on your computer using the CD-ROM and be sure to check to make sure the software that came in the box is up to date (you can find the Dino-Lite website online). After opening the program, connect the microscope’s USB plug into your computer—preferably a laptop you can position close to your turntable. You will have to work your way through the software, which is slightly different for Windows and MAC. Set up via the program’s preferences where you want the pictures you take to be stored, etc.

The LED ring around the microscope lens should light when you connect it to the computer’s USB port. If not click the ring icon you’ll see above where it says “picture/video” and it will light.

Now here’s the difficult part: set the microscope’s knurled ring to 175x magnification and secure it in the stand you’ve purchased (alternatively, you can use a tripod to which you’ve clipped a beam of some kind to which you attach the microscope).

Make sure you start with the tonearm parallel to the platter however you do that (the Graham Phantom Supreme II has a built in spirit level for instance).

Place the shiny side of a CD on the platter so that it protrudes slightly from the platter’s edge and carefully lower the stylus onto it. Then move the arm so the stylus is as close to the CD’s edge as you can manage. Be very careful now!

This is where it gets both tricky and dangerous so proceed with caution and watch what you do! That said, I’ve never damaged a stylus doing this and neither should you, but you have to exercise great care at all times, particularly as you shift focus from the image on the computer screen to the cartridge and microscope.

Now, maneuver the microscope and stand so that the microscope is very close to and parallel to the platter and the center of the lens bisects the edge of the CD vertically, while the stylus and cantilever bisect the lens horizontally. You should be able to see the CD’s edge and the stylus and cantilever as well on the screen. Remember: because of the large amount of magnification, a tiny movement of the microscope produced huge image movement. If the edge of the CD is not perfectly level, re-position the gooseneck or carefully rotate the microscope within the stand’s holder until it is. That is absolutely essential to getting a good picture and an accurate measurement.

If you see only black, try moving the microscope up and down either using the stand’s knurled ring or by bending the gooseneck until you see something!. Again, this part can be very frustrating and you have to be very careful. Once you have the edge of the CD in sight, carefully and slowly move the CD forward and back until the edge is perfectly focused on the screen and dead level.

Next carefully slide the stylus on the CD until it is very close to the edge of the CD so that it too is equally in focus. You should be able to see the tip of the stylus resting on the CD, not from above or below, but from directly on the CD’s edge (I may not be describing this as precisely as either of us would like, but the photos should help). Also make sure the view of the stylus is purely from the side and not angled from the front or rear. And make sure you have the stylus at the very left side of the screen so you can capture as much of the cantilever as possible. A learning curve is definitely part of this experience so don’t get frustrated if you have trouble at first and many times thereafter!

Now, to brighten the background and put the image in better relief, fold in half a small piece of white paper and place it behind the headshell area. Adjust the lighting as necessary to produce the best image—as close to the image provided here.

Now click the computer program’s camera icon and the image will be captured and appear in the gallery on the left side of the window. Click on it and it will open as an enlarged image. On the left side above the photo, type in the “input mag” (magnification) number corresponding to the knurled ring magnification ring on the USB microscope.

You will also note to the left of the picture another window called “magnifying glass”. As you move the cursor over the big photo, you’ll see a greatly magnified version of the image in the smaller window.

Now enable the measuring tool in the dropdown window that will say “Tools Disabled” and select “3 point angle.” It is extremely difficult to describe how to best use this tool, but just play with it because the red lines it draws are easily removed using the “Clear” drop down box.

You can get an approximate SRA by drawing a line through the center of the stylus (for a cartridge with a centered contact patch!) and ending it precisely at the the tip and then one from the tip across the surface of the CD. The software will calculate the angle.

Or you can do it another way. This time beginning by measuring the leading edge angle and then the trailing edge angle (again this works only when the contact patch is centered). You want to end up with a measured angle as shown in the picture below:

Be sure to terminate the angled line right at the stylus tip/CD surface interface. Use the smaller magnifying window to be sure. Write down that angle (here it’s 54.70 degrees) and then clear the picture. Then measure the angle of the other side of the stylus and the record surface (59.38 degrees).

To measure the SRA of a stylus type where the contact area bisects the stylus side, start with 180 degrees, subtract the first measured angle (54.70), add the second measured angle (59.38) and divide by two: 180-54.70= 125.3 + 59.38=184.68/2= 92.34.

Try it a second time and you’re likely to get different results—as I did using the two different measurement techniques. There’s a certain amount of subjectivity to this and also a skill set that depends on the quality of the image you capture and your skills with the tools. At the very least you’ll find out if you’re in the 92 degree ballpark.

There’s another alternative though. If you send Mr. Malewicz your image (wwmalewi@aol.com), he’ll give you the approximate SRA assuming the image is reasonably close to what’s necessary to measure accurately.

Or for $30.00, assuming your image passes his accuracy criteria, he will give you a precise measurement. But that image should look like this and that will take some practice and skill to achieve

If you capture the image correctly and use the software reasonably accurately you will know where your SRA is set within a few degrees at worst, or precisely at best. You'll also find out if your cartridge's stylus/cantilever assembly comes close to spec, or is so far off, you'd have to angle the arm way down or way up to approximate 92 degrees.

That’s all there is to it. (right!)

COMMENTS
alan james's picture

Thanks for posting.  Great read.  

Leefy's picture

Very helpful and interesting post. I am ordering a microscope to try this but have a question about required accuracy as per your photos.

1) As you mentioned, your two measurement techniques gave different results, one at 92.34 and one at 94.83 for the same photo. Is this "close enough for jazz" as far as achieving the benefits of the 92 degree ideal? ie: If my initial measurements show this spread would it be good enough to leave well enough alone?

2) If so, could I safely assume that the "forward tilt" is the critical aspect as long as its in this measurement ballpark and that I should only be really concerned if the measured SRA is 90 degrees or less?

Sorry if I have missed something obvious (It wouldn't be the first time....)

Really enjoying the new site and you have inspired me to improve my vinyl playback. Keep up the great work.

Lee Fitzgerald

Michael Fremer's picture

92 degrees is ideal, 94 is too far forward and the result would be somewhat bright and gritty. But if you start with the microscope and measure 92 and listen and like, note the SRA/VTA however your arm allows that or make a mark on the VTA tower if need be and by moving the post up and/or down by 4mm for a 9" arm, you'll have changed the angle by 1 degree. This way you are at least starting "in the ballpark". <p>

Readers who have tried the microscope have all responded positively...<p>

You can always email the images to Wally for either a free approximation or if the image is sufficiently resolved for his different measurement technique, get an exact measurement for $30. 

Michael Trei's picture

Thanks for the updated info on this method.

I had tried this technique, but gave up due to my inability to get a useful image. I will try the CD and white card reflector idea.

Michael Fremer's picture

Let me know how that works out Michael. 

rlw3's picture

i did not know to remove the plastic guard,  thanks i can now usethe mic i bought 2 years ago.

Martin's picture

Very helpful.

Interestingly, I have the SRA at something over 90 degrees doing it by ear.

It's probably not 92 degrees though, more like 91. Will have to go get a microscope and check.

Mfalcon's picture

Thanks for the post,

Is it possible to use this scope to get a good view of stylus wear.  I imagine this would require some training to do well, but it would further enhance the value of this scope for me.

Mike

deckeda's picture

In the old days your dealer would look at it but even then, a typical jewler's microscoe wouldn't be this strong.

Michael Fremer's picture

According to Mr. Malewicz, an optical microscope is more useful for reasons I don't quite understand at this point. I am trying to get this clarified. Wally says the optical mic with digital camera attached works best. He's sent me some photos that I will post on the site ASAP.

detroitvinylrob's picture

Thank you Michael and Wally for this eye opening and ear delighting knowledge, you guys rock!

I knew CD's would come in handy for something besides drink coasters, who would have ever dreamed that they would actually help you tweak your analog kit?

Taping the turntable plater in several spots so it can't possibly move is a real good idea!

A common CD would need some shimming, at about 1.2mm and a standard 120g (gram) record bring about 1.9mm thick and a 180g record is about 2.85mm, give or take... seems one could get a little closer.

Happy Listening! ;^)>

Michael Fremer's picture

Yes, of course keeping the turntable from rotating is an obvious step. At least to me. I probably should have mentioned it in the article. However, since it takes a 4mm change at the pivot point of a 9 inch arm to produce 1 degree SRA change, I'm not sure it's necessary to be concerned about the CD's thickness...you can always finalize by ear...

ianm0's picture

One point should not be overlooked. The microscope must be absolutely perpendicular to cartridge body to get an accurate SRA/VTA measurement. 

Mikey showed  photos of conventional elliptic stylus. Line contact stylus, like the one from Soundsmith, needs to see different (diamond cut?) axis - instead of the line of symmetry - for measuring the SRA. But it is impossible to see that axis when the microscope is at 90 deg to the cartridge body - one has to move the microscope towards the rear of the cartridge body to see that axis. Doing that gives a larger than real reading. What to do for Soundsmith stylus?

mauidj's picture

I measured the angle using the method described but don't think it's valid for my contact line stylus. Came out to about 112 deg! 

Update.....just spoke with Peter Ledermann at Soundsmith and he told me to subtract 20 degrees from my readings for the conbtact line stylus. So that comes out to 92 degrees...yay :-)

msamji's picture

Thanks MIkey, great instructions. Looking forward to giving this a try! Could we get part 2 to cover how to dial in Azmith with a USB microscope in a future post?  

anomaly7's picture

This is a great article. I now have a reason to buy another toy (microscope) and I get to potentially improve the sound from my cartridge.

tubesorsand's picture

This is solid gold. Not an easy process by any means, but it's something that is hugely important and easily explained by (fairly) simple math. You can spend weeks/months/years swapping out cables made from the purest semi-mono-crystalline 64-karat gold which was carefully hand-refined by classically-educated & well-groomed pureblood Yaks and still not arrive at a guaranteed solution to excellent sound... the subjectivity will drive you to the edge (or past it).

But just like establishing proper gain structure is essential to a recording session, establishing the best possible signal path is vital to audio listening. Thus, being able to set the SRA angle so precisely is what would logically follow the careful selection of a stylus & cartridge. Thank you, Michael and Wally for taking the time to emphasize the necessity of such adjustment and for documenting the method of doing so in such a forthright fashion. There's no voodoo here, but your ears will insist that there must be!

WALLYTRACTORMAN's picture

I  just checked :

-- CD-R  (silver)  thickness is 1.2 mm

-- Std Records  weight -- from 100 to 120  grams --  thickness in recorded area -- from 1 mm  to 1.3 mm

--  180 gr ( checked weight 178 gr) -- thickness  is 2.03 mm --  140 down to 120mm from center

I would not be  concerned about  differences  in above  shown thicknesses -- most important  is to  have Stylus Rake Angle  in the range  91.5 -92.5 degrees

Next -- listen and select  SRA  for most enjoyable sound

Enjoy MUSIC  from Vinyl Forever

mauidj's picture

Dino-Lite AMT313 is an older model though still available from Amazon. I think the AM3013T is the replacement. What others should be considered?

Aloha!

It seems the replacement is indeed the AM3013T. It has a better sensor and color reproduction. There is also an AM3013 which is the same but without the touch sensitive back trigger. The AM3011 is as above but without the measuring ability.

So now you know!

Oh...and they have obviously improved the Crazy glue because I'm still pushing and turning......

Oooops...broke it :-(

Norfolkbarry's picture

What device was used to capture the last image shown? Was that using the suggested USB camera or a traditional microscope with an attached digital camera?

singhcr's picture

Hi Michael,

Thanks for the great article and thanks to Wally (go Minnesota!) for the technical work.

I bought a USB microscope yesterday and found that my current SRA was 94 degrees. I lowered my VTA all the way from 4.5mm to 0mm and got the SRA down to ~93 deg (can't remember the exact angle off the top of my head).

If I am thinking about this correctly, I'd have to increase my VTF in order to reduce my SRA, right? Right now my VTF is 1.45g (Empire 4000D/III cartridge with 2000 series eliptical stylus) and the maximum VTF for that setup is 1.5g. Is it OK to exceed the manufacturer's maximum VTF if I need to? I think my VTF has been lowered anyway as a result of lowering my VTA but I wanted to ask you in case I needed to do that to get to the magic 92 degrees for the SRA

singhcr's picture

I ended up putting a .401mm brass shim at the back of my cartridge to lower the SRA and got a picture with a 92 degree angle as I could not achieve it with increased VTF alone.

I have a bit more tweaking to do as the sound could stand to get a bit more bass (increasing the VTF from 1.45g to 1.5g should help and I lowered the VTA by 1.5mm) but the difference from my initial setup to the 92 degree SRA starting point with the aid of the microscope is simply incredible. The soundstage is so much wider and the sound is incredibly realistic. I can pick out every little detail in the guitars and background vocals and every little nuance in the main vocals. I threw on Journey's Frontiers as it was the first rock record I ever played. I love Perry's voice and it took a while to get used to how different it sounded. I honestly can't put into words how real his voice sounds. I was in shock and eventually in tears. 

Thank you, thank you, thank you!!!

vince's picture

Very interesting article.  I used it to confirm that my Denon 103 was, in fact, set to 92 degrees.  It was, precisely.  My dealer did a great job setting it up.

 

Since then I upgraded to a Shelter 901 MKII.  It sounds brighter (even sibilant) than the Denon and I thought I would get the microscope out and have a look.  With the tonearm parallel to the platter I see 80 degrees, SRA.  Dropping the arm until the back of it hits the record only gets me to about 85 degrees (and a tonearm that no longer works).  Indeed, to get 12 degrees of change from a 9" tonearm will require 1.9" of drop, this is more than the entire range of the VTA on my tonearm.  I can also shim the cartridge by 0.18" to achieve 92 degrees, but this seems pretty extreme.  It seems crazy that a cartridge that costs as much as this one could be so far off.  So I thought I would contact the manufacturing and ask if I am missing something.  The booklet that came with the cartridge doesn't list a contact number.  Neither does the nice box it came it.  A web search doesn't get me anywhere either.  Anybody know how to contact Shelter Inc?  Anybody know if the diamond is ground in such a way that shooting for 92 degrees is actually the wrong thing to do?  I must admit, at this point I feel a bit like I just tossed a tidy sum of money out the door.  

lcross's picture

Whoops, should have asked my question here I think!  So does the 92 degree SRA recommendation hold for monaural cartridges/styli as well Mike?  I've very much enjoyed your articles and comments on this and using the USB digital scope, I've got one being shipped to me now and look forward to perfecting my technique!

 

Larry

mem916's picture

I found a nice Dino Lite AD413-ZTA on eBay for under $200 a few weeks ago.  Spent a couple of days total figuring out how to use it and how best to get repeatable measurements.  The single angle through the middle of the stylus seems to work best for me.  Many records that I thought were somehow of inferior quality were actually fine sounding records after all!

 

Since I have a linear tracking "tonearm" with essentially a headshell and no arm wand (Versa Dynamics) I do see a difference of about 0.7 degrees between thin and thick LPs.  I could set it in the middle and forget about it but you know how it is....

sbtekman's picture

I enjoyed the recent setup demo at T.H.E Show in Newport; the pics and description about SRA adjustment were great! My ZYX Airy 2 uses a microridge stylus and from the reading it appears it is in the contact line family though it often get lumped with 'exotic shapes' like Van den Hull and Geiger,though Geiger is not considered contact line and the SRA for Geiger is taken from the back of the stylus where it contacts the groove , not down the middle as the procedure suggests. I have a digital microscope and got a wonderful pic of the stylus.
An earlier poster said,
"I measured the angle using the method described but don't think it's valid for my contact line stylus. Came out to about 112 deg!

Update.....just spoke with Peter Ledermann at Soundsmith and he told me to subtract 20 degrees from my readings for the conbtact line stylus. So that comes out to 92 degrees...yay :-)"

I tried to find something definitive and its been a fun journey, but Im still unclear.
Should I draw the line along the back edge or down the middle of my microridge stylus to find my 92 degrees?
Thanks!

sbtekman's picture

It was pointed out to me, quite obviously it seems, if my measurement taken down the middle of the stylus produces a wonderful stable image, tonal balance and the tonearm is level, the way zyx prefer, then its correct.

kevemaher's picture

If you have a DSLR with a lens that has a close-up mode (many long focal length zoom lenses have this capability), you can get close enough to get a good image. After that has been saved, I open the jpeg image file with a freeware software program called "ImageJ". to display the image. ImageJ is very easy to download and use. On the toolbar there is an angle function. Set this up and then use the measure function. The angle will be calculated and displayed.
Simple and cheap!

Butch1970's picture

Thanks so much for posting this article!

Just wondering, for those of us just getting into the practice, if the Dinolite that was used back in 2013 is still a recommended choice?

Rudy Merz's picture
music_man's picture

Rudy, does the scope you purchased have software to compute the angle of the stylus? I do not want to spend hundreds on the Dino-Lite scope and as the first thing, begin destroying it.

Bogester's picture

Hi all

The subject of optimising SRA on my system has been something I've been pondering lately. I'm currently running an Ortofon 2M Bronze on my Rega RP6, but I'm not using a spacer to raise the tonearm, so it's "tail down" (slopes downward towards the pivot) by one degree based on the documented height differences between Rega and 2M cartridges. To my ears it sounds great, but I keep wondering if I could squeeze a bit more performance out of my rig by biting the bullet and purchasing and fitting a tonearm spacer. I really can't be doing with that rigmarole if I don't have to, so I thought I'd borrow a USB microscope from a friend the other day and tried to measure the SRA. By my reckoning it's around 91 degrees. I don't know whether Ortofon makes these carts to give a 92 degree SRA with the tonearm perfectly level, but I reckon by adding a 4 mm spacer would both level the arm and give me the "magic" SRA. However, if I do that I know that I won't be able to close the dust cover without it hitting the tonearm counterweight, which would mean forking out for a smaller diameter one (why Rega can't make the dust cover a bit taller to give the tonearm a bit more clearance I really don't know!). All of the this is a gargantuan pain in the you-know-what, frankly. So, finally, to the point of my post. Roy Gandy, in his well-documented and somewhat controversial comments about VTA, reckons that changing the VTF by 0.1 g with a typical cartridge will change the VTA/SRA about 1.5 degrees. Interesting. Has anybody actually verified this experimentally (I forgot to to this before I gave the microscope back)? Could I not just back off the VTF a little (I'm running at the recommended 1.5 g) and get the SRA to 92 degrees? I'd still be within the recommended VTF range if I do this.

Any comments appreciated!

Thanks!

EmmaSampson's picture

I used to be wondering if anyone may want to assist me. I bought some time again a microscope from a shop known as maplin (uk) and i seem to of misplaced the cd which contained the drivers and software program to use it. I've looked on there assignment-help internet site and they appear to have a folder for downloaed which incorporates the drivers. Can everybody inform me please what genuine folder or report do i copy to disk? I have attempted varied ways to copy it to disk but with out a avail.