Cutting characteristic
The cutting characteristic (also cutting characteristic ) is a measure of the lateral deflection of a record groove. At a given speed of rotation of the record and a given frequency , the speed of movement, called the fast , of the scanning needle is not linear, but is adjusted to improve the sound.
The top value
The peak value of the speed of movement is called the fast. This peak value is greater, the greater the deflection (deflection of the amplitude ) and the higher the frequency of the sound vibrations to be recorded.
In order to obtain the most linear frequency response possible, the purely mechanical scanning was cut with constant speed. With decreasing frequency, this resulted in increasingly larger groove deflections, which would have to increase the required storage space on the vinyl. On the other hand, with increasing frequency, the groove deflection would become so small that the useful signal would be lost in the noise during playback . Accordingly, it is practically impossible to record sound with constant speed over the entire frequency response.
For this reason, the cutting frequency response has been determined according to the recommendations of the RIAA and the German standard DIN 45 541. The recording does not take place with a constant speed, but with an in principle constant deflection according to DIN IEC 98, which corresponds to a speed that increases with frequency (height increase). According to DIN 45 533, the characteristic curve of the N78 record had around 4 dB less treble increase at 15 kHz .
Subdivision
| Crossover frequency | Time constant | relative speed |
|---|---|---|
| ≈ 50 Hz | 3180 µs | −17 dB |
| ≈ 500 Hz | 318 µs | −3 dB |
| 1000 Hz | ≈ 159 µs | 0 dB |
| ≈ 2120 Hz | 75 µs | +3 dB |
The cutting characteristic is divided into four sections:
- one below 50 Hz
- one between 50 Hz and 500 Hz
- one between 500 Hz and 2120 Hz
- one between 2120 Hz and 20,000 Hz.
In sections 1 and 3 the speed is constant, while in sections 2 and 4 the deflection is constant. As can be seen from the curves above, however, these sections merge continuously.
The deflections in the low frequency range below 50 Hz are increased slightly in order to achieve a higher rumble-to- noise ratio. The exact course of the cutting characteristic is determined by the transition frequencies mentioned above (usually rounded values) or by the corresponding time constants (exact values according to the specification, except for 1000 Hz). The transition frequency can be calculated from the time constant using the following formula :
In table 1 all important data of the cutting frequency response are compiled. At low frequencies the maximum deflection is given by the groove spacing , at high frequencies by the radius of curvature of the needle on the contact surface. For high and low frequencies, the smallest deflection is limited by the required rumble-to-noise ratio (noise).
| rotational speed | 33 / min | 45 / min |
|---|---|---|
| stereo | 10 cm / s | 8 cm / s |
| Mono | 8 cm / s | 12 cm / s |
In order to get as precise an idea as possible of the speed with which records are cut, record type, speed and speed are compared in Table 2.
With the new development of electromechanical converters , it was possible to optimally adapt the frequency response of the cutting characteristic to the scanning conditions and the statistical distribution of the amplitudes of music and speech and then to equalize electrically .
The cutting characteristic applies in Germany to all records produced. Foreign sound carriers on vinyl often have different cutting curves to which the cutting curve equalizer can be switched ( NAB , RIAA: 3180/318/50 µs, BBC : 3180/318/25 µs, FLAT: 3180/319/0 µs). The different cutting curves are only different above 1 kHz.
See also
literature
- Johannes Webers: Tonstudiotechnik: Sound recording and playback for radio, television, film and record. 5th revised and expanded edition, Franzis Verlag, Munich 1989, ISBN 3-772-35525-0
- Johannes Webers: Recording studio technology. Handbook of sound recording and reproduction in radio, television, film and record. 7th revised and expanded edition, Franzis Verlag, Munich 1999, ISBN 3-772-35526-9
- Michael Dickreiter, Volker Dittel, Wolfgang Hoeg, Martin Wöhr (eds.), "Handbuch der Tonstudiotechnik", 8th, revised and expanded edition, 2 volumes, publisher: Walter de Gruyter, Berlin / Boston, 2014, ISBN 978-3- 11-028978-7 or e- ISBN 978-3-11-031650-6
- Peter Zastrow: Phonotechnik. 4th revised edition, Frankfurter Fachverlag, Frankfurt (Main) 1988, pp. 270ff, ISBN 3-872-34119-7
- Fritz Bergtold: Modern record technology. Pocket textbook on record playback, Franzis-Verlag, Munich 1959 (Radiopraktiker-Bücherei)
Web links
- Plate cut frequency responses (cutting frequency responses) - normal groove plates and narrow groove plates historically, Sengpiel.
- Record cutting frequency response RIAA and time constant calculator Sengpiel
- Further information on the RIAA characteristic curve example
- On the theory of record equalization Andreas Hünnebeck (PDF; 50 kB)
