AnalogMagik Tutorial No. 8: How to set Vertical Tracking Force (VTF)
Vertical Tracking Force
Most cartridge manufacturer will specify a number which the Tracking Force should be set at. More often than not, this number is a range instead of a fixed number (eg. 1.8g to 2.2g on most cartridges). One must never adjust VTF outside of the range provided by the manufacturer, otherwise, damage may result. DO NOT ever deviate from this range. It is NOT endorsed nor recommended by AnalogMagik to go outside of manufacturer's specification.
We have spoken with a number of cartridge manufacturers, and not a single manufacturer or individual was able to provide us with a definite and consistent answer on how to how to determine an exact number except to "go by ear".
As far as we know, AnalogMagik is the first to attempt to propose a methodology on calibrating tracking force scientifically.
We have discovered that changing the VTF will affect the Total Harmonic Distortion differently at different frequencies. For example, if you increase the VTF, the THD% on high frequencies will go up while the THD% on low frequencies will go down. But after a certain level, both sets of numbers will go up again. We have discovered that VTF can be optimized by finding a setting which yields the lowest possible Total Harmonic Distortion across both high frequencies and low frequencies.
The Analog Magik test LP contains two test tracks for VTF calibration, one with a high-frequency test signal, and one with a low frequency. Repeat the measurement by using different tracking force levels. You may discover that different VTF settings will cause the THD% to go up or down between the two frequencies. The optimal VTF is one which yields the lowest set of THD% numbers in both high and low frequency test tones.
We have received enough feedback from users that the optimal VTF can be found using this method in approx. 70-75% of all cases. There are myriads of interference which may interfere with this test method, such as cartridge quality, stylus shape, tonearm bearing chatter, resonance, and other uncontrollable factors. In cases where a correlation cannot be found, more rigorous test methods such as sine wave observation, or using other test tones may be needed. Depending on market demand and returns, we may introduce these in-depth tool in future releases.
Within our labs, we have experimented with a countless number of different distortion tests on different VTF, and we can certainly produce an entire LP with 10 different test signals and perform 10 different sets of test on VTF alone. But if it is too complicated, no one will understand it and very few will spend money on the product. At the end, we have decided to include one test which is easy to use and understand and will likely yield meaningful results.
Lastly, we do not want to discredit anyone who decides to choose a setting most suited for their ears too. We do that too, but that is not a scientifically repeatable method.
We welcome emails on constructive and friendly exchanges of ideas, user feedback or questions.
Field Test Results
Bing R. Tsai, Analog Reviewer of Audio Art Magazine, and the Audio Analytics and Measurement Group, has performed extensive testing on AnalogMagik. One of this reports can be found HERE:
After finished writing the Part-1 of AnalogMagik review (Audio Art Magazine,
July 2018), I started to test the remaining features I haven't spent much time
on. The Tracking Force function are verified on two cartridges here, Lyra
Kleos (recommended VTF=1.73 according to the user manual) and DS Audio
DS 002 (recommended VTF=1.7). Figure 1 is the final VTF for the Kleos after
optimizing for the lowest THD using AnalogMagik. Figure 2 is for the DS
002. For the Kleos which is my main reference cartridge for the past 2+
years, even though the change is only -0.04g from the original setting, the
sound has become much more refined with high-frequency extension
unheard before. Similar improvements are also heard on the DS 002, but
somewhat less drastic even though the change in VTF is much greater.
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