Copy effect

A copy effect in a magnetic recording is manifested due to the fact that when storing a recorded magnetic tape wound on a coil or core, its strongly magnetized portions magnetize the tape in adjacent turns; during playback, such secondary “prints” are perceived as delayed or advanced echo ^[2] . The copy effect is clearly noticeable when the “fingerprints” coincide with the pauses of the main signal; it is especially pronounced in audio recordings of oral speech and theatrical productions, in which short, loud fragments coexist with relatively long pauses ^[2] .

The copire effect level can be from −60 to −30 (in the worst circumstances) dB relative to the level of the “donor” signal. The relative level of the copy effect depends on the composition of the magnetic layer, the tape thickness, the spectrum of the recorded signal, the temperature and storage time, and the magnetic history of the tape ^[3] :

• the smaller the particle size of the magnetic layer, the more intense the copy effect ^[4] ;
• The largest copy effect is observed at frequencies at whichThe wavelength of the recorded signal is 6.3 times the thickness of the tape ^[3] . For example, in compact cassettes (the belt pulling speed is 4.76 cm / s, the tape thickness is 9 ... 18 μm), the maximum corresponds to the frequency 420 ... 840 Hz. At higher and lower frequencies, the intensity of the copire effect decreases sharply;
• the higher the temperature, the higher the copy effect. The dependence of its level on temperature is almost linear: as the temperature rises by 1 degree, the relative copy-effect level increases by 0.3 ... 0.4 dB ^[5] ;
• the longer the tape is stored in the wound form, the higher the copy effect ^[6] ;
• the more time elapsed between recording the tape and winding it on the coil, the lower the copy effect ^[6] . The smallest copy effect is achieved in industrial duplicators, in which the recorded tape is dumped into a spacious container, and only then, when the effects of aftereffect in the magnetic layer of the tape are quenched, is “charged” into the cassettes.
• the more time elapsed between coil unwinding and playback, the lower the copy effect. His "prints" contain both irreversible and reversible components; to remove the reversible magnetization, unwind the tape. For ten minutes, the "prints" weaken by about 3 dB. The ultimate attenuation of the copy effect, about 6 ... 8 dB, occurs in one to two hours ^[7] .

The copying effect in the recording occurs due to the deformation of the wall between the grooves when the maximum permissible amplitude of the recorder's cutter is reached (see RIAA Curve article # Geometrical limitations on writing ).