Vertical Tracking Force (VTF)

The fifth parameter is the Vertical Tracking Force, or VTF. It's also commonly referred to as tracking force and tracking weight. It is defined as the weight measured at the stylus tip, usually expressed in grams. This parameter is more critical than most people might realize, and some cartridges are especially sensitive to this setting. There are two main issues affected by the VTF. The first is the alignment of the magnetic motor system. There are three major methods of creating a magnetic phono cartridge: the moving coil, the moving magnet, and the moving iron. I'll explain each briefly before I go on. The moving coil cartridge has two coils attached to the actual cantilever, usually at a 45 degree angle (to be perpendicular to the groove wall it is meant to reproduce). These coils, when moved within a fixed magnetic field, generate the voltage that represents the musical signal. The moving magnet cartrige has the magnets attached to the canelever. The coils are fixed, and moving the magnets relative to the coils generates the voltage in the coils required for the musical signal. The last method, moving iron, or sometimes called moving flux, uses a magnetic metal, usually iron, which is attached to the cantilever. In this type of cartridge, both the magnet and the coils are fixed in place, and voltage is generated in the coils by moving the iron which modulates the magnetic field picked up by the coil to generate the voltage. As you can see from the descriptions above, each method relies on varying the magnetic field in some way to induce voltage in the coils. In each case, it is important to the proper operation of the cartridge that the magnetic generator be properly aligned. In the case of a moving coil cartridge, you want the coils centered in the magnetic field when there's not groove modulation. Likewise the magnets should be centered relative to the fixed coils in a moving magnet, and the iron centered in the magnetic field between the coil and magnet for moving iron cartridges. VTF also affects the cartridge suspension. The cartridge suspension, like a car suspension, is designed to operate optimally within a certain "load". Overload your car, and when you go over a bump, you can bottom out the suspension. If it's not loaded enough, you get an overly bouncy ride. In a way, your cartridge suspension acts in the same way. Either way, don't go by tracking ability alone to set your tracking force. It is important to understand that the goal is to both align the magnetic generator and to ensure the proper operation of the suspension. Properly set VTF may not result in the absolute best tracking.