AnalogMagik Tutorial No 4: How to set Vertical Tracking Angle (VTA)
(For AnalogMagik Version 1 Users)
Vertical Tracking Angle
The Vertical Tracking Angle generally refers to the angle of the tonearm when viewed from the side. (Technically speaking, it is actually the angle of the cantilever vs the flat record surface). This, in turn, determines the Stylus Raking Angle (SRA), it is the angle in which the stylus is raking the record grooves at.
An excellent place to start the VTA Angle is to visually observe horizontal leveling of the tonearm viewed from the side. If you have a magnifier, or USB Microscope, you can observe the actual VTA Angle of the Cantilever, or stylus raking angle.
Whatever the technical terminology, the result is to achieve the same thing, that is to optimize the angle at which the stylus is raking the LP at, when viewed from the side.
The generally accepted theory is that the optimal SRA Angle is the angle at which the LPs are
cut at, in most cases, this will be 92 degree, but a certain amount of variability is possible. Without a microscope, it is often difficult to observe the SRA, so an approximate starting point will be to adjust the VTA, or the horizontal level of the tonearm to about 15 °.
The Acoustical System SMARTstylus is an excellent tool which will allow you to visually gauge an initial Stylus Raking Angle. The Uni-Scope Magnifier will also allow you to visually magnify the stylus to magnify the stylus 200x on your computer screen.
The theoretical optimal angle of 92° is based on the assumption that this angle will produce the lowest intermodulation distortion (IMD%). Visual methods provide a good starting point, but as soon as the platter start spinning, the dragging force created by the stylus raking on the LP will produce a downward force which will cause the raking angle to change.
Only an actual measurement performed while the recording is spinning will produce the most accurate results. This is unachievable using visual methods.
The AnalogMagik software has a VTA function which allows you to determine the actual intermodulation distortion number and it will be displayed on the laptop screen. Simply fine tune adjust the VTA angle until you reach a level which produces the lowest intermodulation distortion percentage (IMD%).
While performing this measurement, you may discover a small nominal difference between the left and right channel. All cartridges will experience a small difference between channels, this is limited by cartridge quality, and it is not a programming error.
Again, we emphasize that an optimal reading is also affected by Azimuth, Anti-skating, as well as Vertical Tracking Force (VTF), you may need to go back and forth between parameters to achieve an optimal setting across all parameters.
Establishing Correlation & Obtaining Meaningful Results
The most important thing to achieve with the VTA/ASA function on AnalogMagik, is to establish a correlation between VTA/SRA changes versus the results displayed on screen.
AnalogMagik is just a distortion analyzer, it is not guaranteed to deliver a low baseline IMD% number, because a low baseline number has to do with your equipment. AnalogMagik simply display what it reads.
Please note that meaningful results of the VTA/SRA function is highly dependent cartridge quality, as well as the inherent noise level of the entire setup. Our experience is that if the initial observed Intermodulation Distortion distortion is higher than 5-7%, then the chances of establishing a correlation or obtaining meaningful results will be smaller than in cases where the baseline is, say 2-3%.
We have also observed that some cartridges are more sensitive to VTA/SRA changes than others. Some users report a very strong correlation, others report utterly meaningless numbers. So if you are unable to obtain meaningful results, it only means the program is not able to establish a correlation between VTA vs IMD% changes. It does not mean the program is not working, it only means your cartridge is not sensitive to VTA changes, or the baseline vibration level is too high, interfering with the measurement.
We have discovered that a few factors may contribute to a high baseline number or an unstable number:
1) If the measurement is jumpy, meaning if there is a jump in the number of more than 1% between readings, you are likely picking up inherent vibrations which are interfering with the measurement.
2) If a high baseline IMD% number coincides with bad azimuth reading, it is strongly indicative of a small zenith angle error on the stylus Once zenith angle is compensated, we have seen Azimuth crosstalk and IMD% improve dramatically
3) In cases where the resonance frequency of the arm/cartridge combo doesn't fall within the range of 8-12Hz, IMD% usually gives out bad numbers.
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