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??
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Nwright: what came as a surprise was when Stereophile (not Michael) switched around the photos and captions, so that the SRAs and cartridges in the published article didn't match up. Corrections were printed in a follow-up issue.

FWIW, there never has been any published industry standard for SRA. The sole documentation supporting the 92-degree SRA that I have been able to find - in any language - is the Jon Risch article, and that never became part of any industry standard. What does "mounted correctly" mean if there never was a standard?

There is more of a standard for VTA (originally 15 degrees, which is where Shure's "V-15" name comes from, later gradually revised upwards until it became 20 degrees) than there is for SRA, but even so, some cartridges (both present and vintage) deviate from this significantly. On the Vinyl Engine website, Werner Ogiers collated a VTA table for various cartridges from various manufacturers, based on measurements made by HiFI News & Record Review magazine (rather than manufacturer's specifications):

http://www.vinylengine.com/turntable_forum/viewtopic.php?t=34909

You can see that even industry heavyweights such as Ortofon or Denon made cartridge models with 28 or 30 degrees.

Raul, in the "Who needs MM/MC" thread, didn't you write that some cartridges sounded best with the back of the tonearm raised quite high up? Do you still believe this to be true, or do you feel that improvements to your system and testing methodology since that time may give different results?

Also, did you ever try to measure what SRA you had when the cartridges were adjusted to their best-sounding position?

As a general message (not addressed specifically to Raul), rather than attempting to force all cartridges into a single SRA "standard" that never existed to begin with, it would be far more useful for both manufacturers and audiophiles if audiophiles would align the cartridges to their best-sounding position, measure the resulting SRA (and VTA), and the various real-world experiences could gradually be collected into a single table for further study.

OTOH, regarding overhang, due to decreasing linear groove speed towards the record label, the frequency response of an LP changes with groove radius, and so does distortion. The upper frequency response falls the closer the groove being played is to the label, while distortion increases.

At the same time, many classical orchestral works have their most dynamic climaxes at the very end of the LP, where distortion is highest and upper frequency response most suppressed. 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.

kind regards,
Jcarr said:
At the same time, many classical orchestral works have their most dynamic climaxes at the very end of the LP, where distortion is highest and upper frequency response most suppressed.

That is why the Classic Records RCA reissues in 4 single sided LP's are so good. You stay far away from the dreaded label, besides the other benefits of 45 rpm vs 33.
I have been chasing this 92 degree thing off and on for a year or so with fair results. Basically, when I've checked the two carts I've had for SRA after setting them by ear the results are not far off that 92 number. BUT, when one of the premier cartridge manufacturers says there is probably not much validity to this concept, I think I may relegate my USB microscope to the closet.
http://i3.photobucket.com/albums/y57/WntrMute2/9fcaa181cb084a96e99991e54887c11e_zps43ed330b.jpg
http://i3.photobucket.com/albums/y57/WntrMute2/ScreenShot2012-10-12at91619AM_zpsf582ed48.png
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.
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