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Stylus Rake Angle

I am trying to set up my new VPI 3D arm as close to perfection as I can. On the Analog Planet, Michael Fremer gives one opinion, however, a different opinion was voiced by Harry at VPI, and Peter at Soundmith. I've been discussing this with them....Fremer says that SRA should be adjusted even if the back end of the arm is WAY high up as needed, whereas Harry, and Peter said to start with the arm in a horizontal position and move it slightly up and down to find the sweet spot. Peter said that my cartridge (Benz LPS) and some others have an additional facet in the diamond so bringing the arm up in back would be exaggerating the proper SRA. When I wrote back to Fremer, he answered with an insistance that he was correct. Does anyone want to add to the confusion??
stringreen
csontos
1,311 posts
 
Has the fact that both VTA and SRA measured angles change as soon as the stylus is loaded been mentioned? Also, this load changes with the depth of the groove causing more or less friction. The more cuts crammed onto the record the shallower the groove. Not only that, but the angle of the cutting stylus which is typically set up and adjusted by the particular technician at hand, varies from shop to shop,(even within the same shop), brand of machine, and specific cutting bit. The actual SRA issue is moot because of the variables. It's only valid for the sake of conversation. 'Around 92 degrees', or so. A tone-arm without adjustable VTA on the fly is imo, inferior. You've got to tune in every single record.
jcarr
385 posts
 
Wntrmute2: IMO, visual observation of SRA with USB microscopes is not a waste of time - if it is being done correctly (which I have found is another very big if). But as I wrote above, 92 degrees was never an industry standard. Even the Jon Risch article that is the sole published article on a 92-degree SRA, acknowledges that SRA when cutting LPs can vary from 91 to 95 degrees, which tells you that 92 degrees in the original article was a chosen as a "one-size-fits-all" number convenient for publication.

There are a variety of reasons on the LP production side, cartridge fabrication side, and optical measurement side why 92 degrees may or may not be "it".

At this point in time, I believe that it is best to let the ears guide and the optical measurements follow, rather than the reverse. If measurements in hundreds of audio systems begin to suggest that 92 degrees is indeed the magic number, than cartridge manufacturers such as ourselves can seriously think about reshaping our stylii and cantilevers so that best sound is achieved.

I suspect that optical measurements of a hundred cartridges that are set up for best-sounding SRA are likely to show a bell-curve, with the majority coverging on whatever the magic number is, but with a reasonable number of outliers in both the positive and negative direction.

Keep in mind that whatever angle specified by the designer, however, it will be subject to manufacturing tolerances, and some cartridges may still look "odd" when the SRA is set to 92 degrees. Also, with the USB camera lens so close to the cartridge, there is a fair degree of optical distortion and subjectivity involved in interpreting the photos taken.

Here are two more links that you should study and think about before jumping in the 92-degree bandwagon (especially my second post):

http://www.whatsbestforum.com/showthread.php?536-The-importance-of-VTA-SRA-and-Azimuth-pics/page13

http://www.whatsbestforum.com/showthread.php?536-The-importance-of-VTA-SRA-and-Azimuth-pics/page14

This link discusses how vital it is to be absolutely spot-on if you try to take stylus photos with a USB microscope.

http://hifiheroin.blogspot.jp/2012/09/know-your-angles-new-toy.html

And this link describes how a Kleos customer deliberately ripped off the washi paper coil protector and damaged the cartridge dampers in his attempts to drop the SRA to 92 degrees. Kind of a tragedy-comedy.

http://www.analogplanet.com/content/have-we-opened-digital-can-worms-recommending-using-usb-microscope-set-sra-stylus-rake-angle

hth and kind regards
rauliruegas
13,129 posts
 
Fear J.Carr: Yes, a few years ago testing Empire cartridges ( I think the 900/1000GT and the 1000 Z/xe. Other cartridges I can't remember. ) I found out that performs the best at " odds " high up cartridge tail/back of tonearm.

I did not tested again since then. But now that you brought here the subject I will try to do it and report my findings. I have to tell you that those VTA/SRA experiences made me to disappear the " afraid " to have that kind of " high up " VTA/SRA. I have to say too that with some today and vintage MM/MI/LOMC cartridge and when I use that high up kind of set up what we can hear from upper mid frequency range and up can be outstanding but unfortunatelly with detriment on the bass management quality performance and perhaps?? higher distortions in the former/that frequency range ( but I do not know for sure because the experience is so different/new. ).

In the other side and know that you asked: I'm just starting to include in my cartridge tests the SRA measure, I'm only waiting for the digital micro arrive.

Btw, I'm with you about try to have a table/chart with all those audiophile experiences with any cartridges where each one report on the SRA measure where we set up the VTA/SRA because was the position that we " like it " and not because it measure that 92 number that as you I still think means almost nothing and certainly is not and is far away to be the industry standard till that can be proved. That chart/table will help to cartridge manufacturers as you are to be " spot on " in the whole subject.

+++++ " For this reason, you should not choose your cartridge alignment (Baerwald, Lofgren, Stevenson, modified versions of these) without considering how close the groove extends toward the label on the LPs that you prefer, and how dynamic and complex the musical content is at the innermost groove positions. " +++++

as almost always there is no perfect alignment ( for several reasons as the one you name it. ): trade-offs always exist and something that helps a lot to lower distortions in the inner LP grooves ( other that the kind of alignment choosed. ) is to choose a cartridge high trcaking abilities and here you cartridge designers/manufacturers are the ones that have the " last word ".

Regards and enjoy the music,
R.
sarcher30
596 posts
 
I think 92 degrees SRA as a starting point is better than just setting the arm to level and having no idea what the SRA is. Adjust for best sound after that. You should get more consistent results adjusting between various different carts by starting at 92 degrees.

Even though there is no standard for SRA, 92 degrees seems to be the middle of the range for what records are cut at. To me it would be logical for a cart designer to shoot for 92 degrees when the tonearm is level if possible. That way it is easier to get to whatever SRA sounds best within the adjustability of the arm.

I think it would be a good thing to have a standard but it is probably a little late in the game for that. I wonder if modern reissues are all pretty much the same SRA or are they still all over the map?

As said before in this thread it is not possible to get an accurate reading of SRA using a microscope unless you are lined up perfectly due to the curvature of the optics. How one knows they are lined up perfectly I do not know. I have very good close up vision and trust it more than my results with a USB microscope. My far away vision is another story though. ;)

Sean

don_c55
1,025 posts
 
Whatever your starting point, level or 92 degrees, the actual SRA arm height range is very, very small! Adjust "on the fly" is worthless, because you will pass over this very narrow peak with a quick adjustment. You must "zero in" over time, to find the optimal spot, and reset azimuth and VTF as you go. Note sonic changes throughout this process, as it is a learning experience.

On my VPI JMW 10 the final sweet spot "window" is plus or minus one index mark on the Micrometer head height tower. This is a range of +/- 3 10,000 of an inch!
Without a micrometer head on your arm, I doubt you will find this optimal SRA spot.

Once I find this "sweet spot point" after listening to many Lp's, over a few weeks or months (after break-in is complete), I do not change the height. 95% of my records are of "normal" thickness, so I do not readjust height for the 180 gm Lp's.

I find I get super playback quality on 80% of my Lp's with this one setting.

One must also take into account recording quality variation, as some Lp's just sound "off" regardless of SRA setting. The resolution of ones system must also be acknowledged for your personal results. Adjusting for each Lp is too "anal retentive" for me!
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