IEC 60098-2020 ANALOGUE AUDIO DISK RECORDS AND REPRODUCING EQUIPMENT.
4.1 Scales for graphical presentation of data Linear or logarithmic scales are recommended for graphical presentation. Linear decibel scales are equivalent to logarithmic scales. Other kinds of scale, such as double logarithmic, should be avoided. When using decibel scales, the zero reference should, if possible, be the rated value. In those cases, where each of the scales refers directly to physical units, it is recommended to avoid a combination of linear and logarithmic scales. Where quantities represented by the axes are of the same kind, it is recommended that the same unit length be used for both. Linear scales with remote zero point should be avoided as far as possible. For further information, see IEC 60263.
4.2 Scales for frequency characteristics Graphs should be drawn with frequency in Hz on the x-axis with a logarithmic scale, and the level expressed in dB on the y-axis with a linear scale. The scale ratio should be such that the length representing one decade of frequency is the same as the length representing a 25 dB or a 50 dB difference in level. The preferred length per decade is 50 mm. If the size of the graph is changed, the scale ratio should be left unaltered.
5 The disk
5.1 Types of disk records The types of disk record given in Table 1 shall be standard.
5.2 Dimensions of disks
The dimensions for types 30xx and 25xx are shown in Figure 1 .
5.3 Unbalance of disks
The centre of gravity of disks having a small centre hole shall lie within an 8 mm diameter circle concentric with the centre of the centre hole.
5.4 Direction of rotation The direction of rotation of the disk shall be clockwise when viewed from the side being reproduced.
5.5 Direction of recording The direction of recording shall be such that, on reproduction, the pickup shall travel as closely as possible along a straight radial line towards the centre of the disk.
5.6 Speed of rotation The speed of rotation during recording shall be within ±0,5 % of the rated recording speed, the rated recording speed being such as to give the intended musical pitch at one of the following rated reproducing speeds:
• 33⅓ r/min: for disk record types 3033, 2533 and 1 733,
• 45 r/min: for disk record types 3045, 2545 and 1 745. NOTE Verification of reproducing speed by means of stationary stroboscopic bars in countries employing 50 Hz electric supplies can be made at 45,1 1 2 r/min only.
6 The groove 6.1 Direction of groove modulation The stereophonic groove shall carry two channels of information. The two channels shall be recorded in such a manner that they can be reproduced by movements of a reproducing stylus tip in two directions at 90° to each other, and at 45° to a radial line through the stylus tip and the centre of the record; these movements shall be tangential to, or lie in a plane through the stylus tip and the record centre, inclined at an angle of +5 0 20 ° anticlockwise to the normal to the record surface through the stylus tip as viewed towards the record centre (vertical tracking angle). The resulting modulation shall be optimum for reproducing styli having a rake angle of between 0° and −5° (for detail, see Figure 3).IEC 60098 pdf download.