Her har jeg sakset litt fra Leif Häggmark (konstruktøren av Airtangent armen) sitt syn på justering av VTF:
"Test records often include 'tracking test' bands, usually comprising a single frequency tone at around 300Hz, cut at progressively higher levels. Separate lateral and vertical modulation bands are commonly provided, as a cartridge's tracking performance on vertical signals is usually markedly worse.
Because these tests are conducted at a single frequency they give a limited assessment of a cartridge's practical tracking ability. Worse, they are often used as a method of setting tracking force, an approach which favours downforces at the top of the cartridge's specified tracking force range, at which its tracking will be best. This can have an undesirable effect on other aspects of a cartridge's performance: many display a bass-heavy tonal balance and generally lacklustre sound if tracked at high downforces. It is therefore better to set the optimum tracking force by ear, within the cartridge manufacturer's recommended range."
Videre sies det fornuftige ting om VTA:
" VTA/SRA
In conventional cartridge design the stylus is attached to a cantilever which is pivoted within the cartridge body, some distance above the record surface. The vertical motion of the stylus is therefore not at right angles (or 'normal') to the record surface. A tangent to the stylus' vertical arc of motion at record level makes an acute angle to the normal to the record surface, and this is called the vertical tracking angle, or VTA for short.
In much the same way that distortion results from lateral tracking error, if the VTA does not align with the orientation of vertical modulation on the record (called the slant angle) the stylus follows a `skewed' path, distorting the vertical component of the groove modulation. This distortion will be most prevalent on sources to the left and right of the stereo soundstage, and on out-of phase ambience information.
A second and less widely publicised aspect of a cartridge's accurate tracing of vertical modulation is the stylus rake angle, or SRA. This is the angle that the vertical axis of the stylus' footprint makes with the record surface; it should coincide with the orientation of the cutting edges of the cutting stylus that formed the groove in the master lacquer.
VTA and SRA are illustrated in the accompanying diagram 12.
Slant angle and VTA are both now standardised at 20° (previously it was 15°). That bald statement hides many ifs and buts, however, which are hinted at by the large error limits allowed in the standards: plus or minus 5°.
The difficulty in accurately specifying a record's slant angle arises from the fact that it is not defined only by the geometry of the cutter. The elastic properties of the master lacquer cause springback after the cutting stylus has passed, and this reduces the effective slant angle. It is the degree of springback that is the source of the uncertainty, since numerous variables are involved: the constitution and age of the lacquer, the temperature of the cutting stylus, the groove modulation and the linear groove speed are a few. The latter two vary with the programme and with position across the record respectively, so that there is not even a consistent slant angle for each record.
The rake angle of the cutting stylus is set to ensure clean removal of lacquer chip, the swarf cut from the lacquer. It is usually between 2° and 5° off a normal to the lacquer surface.
An important matter to bear in mind when experimenting with VTA/SRA is the influence of tracking force. With a cartridge of medium compliance, a change in downforce of 0.2gram will alter the cartridge's VTA and SRA by about 2°, which is equivalent to varying the arm height by 8mm."
