This cartridge was sent to us here at WAM Engineering for microscopic and electrical analysis. The owner wanted us to determine the native Stylus Rake Angle (SRA), ideal azimuth angle and zenith angle of this cartridge. See more about it HERE. We found SRA and zenith to be essentially perfect (92.35 degrees and 0.2 degrees respectively) but the ideal azimuth angle was 2.6 degrees off level!
(Azimuth Angle is the angle observed when viewing the cartridge from the front)
While this amount of variation from level is one of the more extreme we have seen for azimuth, let it be known that this cartridge was certainly one the most wonderful sounding cartridges we have heard to date. If the azimuth angle on THIS cartridge was a cause for sonic deterioration, we certainly didn’t hear it!
WHAT IS CARTRIDGE AZIMUTH AND WHY WOULD I WANT TO OPTIMIZE IT?
We’re feeling too lazy to write about something that has been well covered before, so for this point check out Michael Fremer’s excellent two-part article HERE and HERE. Please read these if you are not familiar with what azimuth is and how to measure for it and then come back to this blog post when finished. If you are already familiar, read on!
There are two elements of Mr. Fremer’s articles deserving mention here:
The two most common ways to “adjust” azimuth for its ideal setting are not at all worthwhile methods. Both the approach of visually leveling the cartridge AND the approach use of a mono signal with one channel out of phase and listening for lowest output are both flawed methods for different reasons. The first approach assumes too much about the cartridge assembly and the second has nothing directly to do with the real benefit of getting your ideal azimuth angle dialed in – minimizing and balancing crosstalk!
The ideal azimuth angle of a particular cartridge is a function of two geometric relationships:
The angular relationship of the stylus groove contact surfaces with the cantilever. Ideally, the left and right channel contact surfaces will be at a 45° angle (clockwise & counterclockwise) to the vertical axis of the cantilever.
The angular relationship of the vertical axis of the cantilever to the coils. Again, the coils should be at a 45° (clockwise & counterclockwise) relationship to the cantilever.
If you want the widest, deepest and tallest soundstage with the greatest separation of instruments in space with pinpoint, stable imaging then you’ll spend the effort to optimize your azimuth. See THIS ARTICLE in WallySchool! to learn more about this.
WHAT IS AN ACCEPTABLE VARIATION OFF LEVEL TO ACHIEVE IDEAL AZIMUTH ANGLE?
Cartridge manufacturers work with a certain amount of necessary and acceptable variation from the designed geometry in the construction of their cartridges. The acceptable amount of variation from the design targets is called tolerance. When any part is out of alignment beyond the tolerance limits, that part is faulty and should be repaired or replaced by the manufacturer. For our purposes here, the primary geometric relationships to be sensitive to are the coil mount angle (ideally 45° off level with the top surface of the cartridge for each channel's coil) and the "vertical stylus orientation" (stylus is ideally mounted perfectly vertically on the cantilever which will allow it to sit perfectly perpendicular to the record surface.)
It is the coil mount angle will determine at what azimuth angle the cartridge will be tilted at to achieve maximum stereo separation. The stylus orientation will determine how well the cartridge tracks the groove. Again, more on this HERE.
The part of the stylus that actually touches the groove is not a straight line but is a curved portion of the stylus called the major radius.
The smaller the radius is, the more the cartridge is forgiving to being on an angle in the groove. The larger the major radius gets, the more it begins acting like a straight line and does not like to to have the stylus orientation at an angle off of perfect perpendicularity with the record surface. When severe enough, a tilted stylus riding through the groove can become a cause for audible mistracking.
So, you can see the question of how much of an azimuth angle is too much is highly dependent upon your stylus profile. Worse, if the coil mount angle erred in one direction and the stylus orientation erred in the opposite you could conceivably have an azimuth angle of, say, 3 degrees but the stylus orientation might be perfectly vertical in the groove at that point. Sorry, but there are no standard answers here but perhaps we can offer some guidelines.
Generally, we’d suggest a conversation between the owner and the dealer or manufacturer of any cartridge that is >2.5° off level at its measured ideal azimuth. If you have a cartridge that had to be angled by 2.5° to 3.5° to achieve maximum stereo separation you might expect the manufacturer to ask to have a close look at it for themselves. If it is off by 3.5° or more we would certainly expect it. Owners of elliptical styli can play looser with these figures but owners of fine-line contact styli with a major radius of greater than about 50 microns should expect no more than about 3.0° to be acceptable.
Listen for audible mistracking if you are on the edge of these figures and see for yourself. Since there can be many causes of mistracking it only becomes relevant as the angle is made more severe. In other words, if you don't hear mistracking at 2 degrees but you hear it at 3 degrees then that is a good indicator the mistracking is a result of a poor stylus mount. You can always inspect the stylus mount using a good microscope to see and measure the angle for yourself.
Based upon what we have seen and measured, you should not expect that just because you spent multi-thousands on your cartridge that the stylus/cantilever/coil assembly should be perfectly aligned. We have seen MANY cartridges come through for analysis and we know it generally does not matter if you paid $1,000 or $21,000 as they all exhibit mounting tolerance errors that often have no correlation to their price tag.
It is important not to guess at your azimuth angle if you are going to begin a discussion with a cartridge manufacturer in which you are bringing their Quality Assurance practices into question. The WallyReference offers an easy, quick and very accurate method for measuring azimuth and SRA angles.
It is certainly to your benefit to KNOW your critical stylus/cantilever/coil assembly parameters and align the cartridge with those tolerance errors compensated for. It is our job at WallyTools to make that possible for you.
Enjoy Analog Forever!