AnalogMagik Tutorial 3: How to Set Azimuth on Your Cartridge.
Azimuth refers to the horizontal balance of the cartridge when viewed from the front. This, in turn, determines at which angle the stylus sits on the record groove.
The theoretical assumption is that when the Cartridge is perfectly perpendicular to the record groove, the stylus will sit perfectly in the record grooves. Visual methods using tools such as the Acoustical System SMARTStylus (an acrylic block with grid lines) or bubble levels offers an excellent starting point.
All cartridges are made by hand and therefore, the stylus may not actually be perfectly perpendicular to the cantilever, the coil assembly at the of the cantilever or the cartridge body. This means visual methods, can only provide you with an approximation. As soon as the record spins, whether your stylus is sitting at the optimal spot is unknown, so it is impossible to achieve an accurate setup by eyesight.
If azimuth is set incorrectly, the Stylus will not sit perfectly in the record groove, signals recorded on the Left Channel will leak to the Right Channel, (or vice versa), this is leakage between Channels is called Crosstalk, and it is expressed as a negative decibel number. The higher the negative number, the lower the crosstalk, the better the channel separation.
Incorrect azimuth will also lead to degradation in other measurements such as %THD between L and R channel, as well as IMD% (Intermodulation Distortions).
All cartridges have some inherent crosstalk, but there is no universal standard on what is considered acceptable. Based on our observation, the crosstalk number usually range between -20 dB to -30 dB.
The AnalogMagik software and test LP contain two test tracks which all allow you to determine the level of crosstalk between two channels. To determine the optimal azimuth, take readings of the two Azimuth tracks on the test LP, and AnalogMagick will compute the Crosstalk number for you.
If Light channel Crosstalk number is > than the Right channel, twist the cartridge by slightly (by approx. 0.5 to 1 degree), and repeat the measurement, or vice versa for the other direction. An optimal Azimuth setting is achieved when the difference between the L and R Crosstalk numbers are as small as possible.
For Example, if you start off with -25.5dB on the left and -28.5 dB on the right, you adjust the azimuth and the numbers will change. Keep adjusting and measuring until the Crosstalk number is as close together as possible, .to say -27.5 and -27. How close a number can be achieved between L and R channel depends on the inherent quality of the cartridge, and is affected by:
zenith angle of the diamond (whether the diamond is mounted perpendicular to the cantilever
the relative position of the cartridge coil versus the stylus tip and the cantilever
AnalogMagik is just a distortion analyzer, it will show you changes between L and R channel as you perform adjustments. It will not magically give out good numbers beyond the capability of the cartridge itself, nor will it do adjustments for you.
On some cartridges, it is possible to achieve a number that is as close as 0.5 dB between Left and Right Channel. On others, you can sometimes get as close to within 1-2 dB difference between channels. AnalogMagik will not adjust the cartridge, it will not correct the channel separation specifications because that is a mechanical issue with the cartridge. That is the job of the cartridge manufacturer, not AnalogMagik.
Some cartridges have an imbalance to begin with, and no amount of adjustment will yield optimal results. Some cartridges have zenith errors which will require changing alignment geometry which will affect other parameters, in such cases, we consider it a manufacturing defect.
There are several important factors which one may pay attention to when adjusting Azimuth:
1) One should never tilt the cartridge beyond 1 to 2 degree.
On a properly built cartridges, the cartridge should not have to be tilted beyond 1 to 1.5 degrees to achieve optimal crosstalk numbers. In most cases, the optimal number falls within 0.5 to 1 degree. If you find yourself having to tilt the cartridge more than 1 to 1.5 degrees to achieve optimal crosstalk, it is very likely that (1) other parameters are set incorrectly because all parameters are inter-related (wrong Anti-skating, wrong VTA Angle, wrong alignment), or (2) The cartridge has inherent imbalances, which is a mechanical issue of built quality. In such cases, it is an equipment limitation.
If your crosstalk analysis leads you to have to tilt the cartridge by more than 1-2 degree, the cartridge is tilted too much and will likely throw off the other parameters. Over time, it will also cause suspension problems due to weight imbalance.
2) Landing Behavior
Azimuth is highly affected by "Landing Behavior" which we talked about in the Basic Alignment Tutorial. If your cartridge has uneven pressure exerted by a cantilever landing behavior which is not going straight up and down, chances are you will never achieve a satisfactory Azimuth Crosstalk reading.
3) Azimuth cannot be set independent of VTA and Antiskating.
Due to the offset angle of headshells, as soon as you change VTA, geometry dictates that it will cause the horizontal level to change, ie) As soon as you change VTA, Azimuth needs to be reset.
Azimuth is also highly affected by Anti-skating and VTF (Vertical Tracking Force). If Antiskating is set incorrectly resulting in uneven pressure on the groove walls, this will often (but not always) cause an imbalance to the Crosstalk numbers. Therefore, you should try to optimize Anti-skating in order to achieve an optimal Azimuth setting. Changing VTF and VTA may also affect Crosstalk to you may have to go back and forth between different parameters and find an optimal point which results in a good set of numbers between all parameters.
4) Incorrect Zenith Angle on Cartridges, or incorrect coil angle at the end of the cantilever.
Zenith angle refers to the angle in which the diamond is glued onto the cantilever. Sometimes it is not perfectly straight, it actually happens quite frequently. Or the coil at the end of the cartridge may not be mounted perpendicular to the stylus.
If there is an inherent imbalance with the cartridge or zenith angle errors, the program CANNOT fix that for you. It is a cartridge problem. But there are things we can do to compensate.
When you are setting up Azimuth, sometimes you will notice no matter what you do, the crosstalk numbers between L and R will not come together. Usually (but not always), we will also see:
Crosstalk between L vs R reading remains far apart (say 5-6 dB difference)
VTA (IMD% above 10%)
This behavior is highly indicative of incorrect zenith angle on the stylus diamond tip, and measuring phase angle will NOT solve this problem. You can use a 200-400x Microscope to examine the zenith angle on the stylus (whether the diamond is mounted straight on the cantilever, or is it off-axis), but the problem is a visual observation on a microscope, is difficult to transpose the degree angle to actual adjustment.
Incorrect zenith angle will result in an incorrect alignment geometry even though the cantilever may be aligned correctly to the gridlines of your template. The way to fix this is to change the alignment geometry (you can try going from Baerwald to Uni) which will rotate the cartridge slightly clockwise if you look at it from the top. By trial and error and patience, you will begin to notice the Crosstalk number will narrow.
In airplane terminology, changing the "Roll" would be changing the azimuth. Changing the Pitch would be changing the VTA, changing the Yaw would be changing the Alignment angle.
To compensate for zenith angle errors, you change the Yaw angle. The difference between Baerwald, Lofgren or Uni, is a change in Yaw angle of the cartridge.
For example, I once mounted cartridge with a crosstalk number of -20 vs -30 dB, 3dB difference between channel and IMD% of 12%. After adjusting for zenith angle error by changing alignment angle, the cross talk came much closer together, -25 vs -25.7 (0.7 dB between channel), channel imbalance is now less than 0.5 dB, and IMD% lowered to 5%.
With more patience and fine adjustment, the numbers will likely narrow to within 0.5 dB on crosstalk. VTA IMD% will likely come down to 2-3%.
When numbers do not make sense, it takes patience. It will make sense when all inherent errors with the cartridge, Tonearm, has been accounted for. Visual methods can NEVER achieve this level of accuracy.
If the cartridge is good, you can achieve readings as good as less then 0.3-0.5 dB between channels, on a very very good setup. On an average setup, you should be able to achieve 0.5-1 dB between channels.
Also, an optimal setup optimizes readings across ALL parameters, it is a balancing act. Do not be pre-occupied with 1 bad reading. Sometimes it is caused by equipment/cartridge limitations and not your setup abilities, or AnalogMagik.
In rare instances where a correlation cannot be found, the AnalogMagik software also allows you to detect the phase shift as well as amplitude difference between the L and R channels, as a secondary measurement. You can adjust azimuth until the phase shift number is as close together as possible. However, this is not a very common occurrence and Phase shifts bear a weaker correlation and it is sometimes not repeatable unless if we incorporate a lot of averaging to stabilize the number. In our opinion, Crosstalk/%THD, measurement is usually sufficient.
Again, an accurate analog setup is a balancing act between ALL and not just one parameter. The goal is to obtain optimal numbers in as many parameters as possible, so do not sacrifice one parameter at the expense of all others. This is why an All-In-One tool is so important because no parameter can be optimized on a stand-alone basis.
4) What numbers to look for?
For the Azimuth Crosstalk measurement, you are trying to equalize the numbers between L and R channel. The goal is not to try to achieve an absolute value of specific target. If you cartridge specification says 36 dB Channel Separation, it does not necessarily mean you will see -36dB on L and -36.5 dB on L. In fact, a lot of cartridges registers numbers below 30dB. This is your cartridge's limitation and a deviation from specification. There is no need to contact the manufacturer.
The goal of this test is to get the number between L and R channel by less than 1 dB, or as close together as possible.
A FAQ on Azimuth:
I tried the Azimuth Function, and I find slightly different results when I use other tools or other test LPs?
Most test records on the market use 140 grams LP, so the number you see will correspond to 140-gram records. Our record is 180 grams, this will cause a change in Azimuth because VTA, as well as VTF, has changed.
Our programming also incorporates algorithms to account for the imperfections of the LP format, including slightly off-centered spindle holes, slight warpness as well as the effect of Wow & Flutter. Do not be surprised if you see slightly different results because almost all distortion analyzers do not take these factors into account.
We also do not advocate using Azimuth as the sole reference and stand-alone parameter as the ultimate determinant for setup accuracy. A true accurate setup takes into account VTA, VTF, Anti-skating as well as alignment, there fore the optimal setting should take into ALL other parameters, rather than just over emphasizing on Azimuth. You have to go back and forth between all test parameters rather than treating them independently.
You will find that Azimuth's optimal setting will be different when you have optimized Anti-skating, VTA, and VTF, so do not be surprised when you see slightly different results.
In an ideal world, all test LPs are accurate. In reality, nearly all test LPs are slightly different in terms of thickness, groove distance, cutting angle, etc. We believe our test LPs are accurate, and we have verified our test signals to the best of our abilities and verified by world class recording engineers and sound producers.
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