At present, the circuits of DC magnetic bias and DC erasure are rare. The following only takes the AC magnetic bias and AC erasure circuit as an example to analyze the disadvantages of the magnetic bias and erasure circuit.

No erasure with recording distortion. Defect analysis and inspection methods. When the AC magnetic bias oscillation circuit is damaged, because there is no oscillation signal output, the recording head will have no magnetic bias current to form recording distortion, and the erasing head cannot erase because there is no erasing current. For this defect, first check the DC operating voltage of the bias oscillation tube with the voltage method, and then check whether the resistance and capacitance in the circuit are open circuit and damaged. If there is a vacuum tube millivoltmeter or oscilloscope, check whether there is oscillation signal output. Defect causes and treatment methods. If the recording and playback switch is in poor contact, it shall be cleaned or replaced. The open circuit and damaged oscillation coil, resistance and capacitance shall be re welded or replaced. Defect analysis and inspection methods. Because this disadvantage requires only one channel, it shows that the operation of the oscillator is normal. Therefore, the disadvantage lies in the bias current supply circuit of the defective channel. Check the bias current trimming resistance and bias coupling capacitor for open circuit or damage.

Because there are many kinds of magnetic bias and erasure circuits, it is necessary to find out the defect phenomenon and circuit structure before repairing the defects, so as to repair them pertinently. In the AC bias and AC erasure circuits, there are some shortcomings in the super audio oscillation circuit, which will make the bias current and erasure current abnormal. Abnormal magnetic bias current will cause some disadvantages, such as light recording, recording distortion and noise. Abnormal erasing current will cause such disadvantages as no erasing, unclean erasing and high noise.

Skill

The words such as clarification, narration and heart monologue are generally recorded in the later dubbing even in the films with the same recording technology. Generally, in order to distinguish the speech of the same period, the later dubbing speech such as clarifying words, narration and heart monologue can be recorded separately on one vocal cord. The dubbing of clarifying words or narration is mostly undertaken by actors with professional speech practice. The volume is stable and the timbre is simple, so the condenser microphone or moving coil microphone can pick up at a close distance. In addition to all the later dubbing films, the dubbing of the heart monologue generally selects the characters in the films of the same period. Generally, in this recording method, a heart-shaped condenser microphone or a moving coil microphone is used for short-range pickup, and there is no need to deal with the sense of distance and space. However, in some cases, the monologue needs to have spatial characteristics, which can generally be completed by using a digital delayer.

Problems of post dubbing

Although the late dubbing has some advantages, there are still many disadvantages from the perspective of artistic creation. The following are some common problems in films with post dubbing Technology:

Incorrect mouth shape

The voice of the actor's voice is not allowed to cooperate with the mouth shape of the picture.

Solution: advance the basic skill level of dubbing actors; After the arrangement skills, the words are adjusted in front and back directions.

Article source: Jiangmen recording production http://www.sjttv.com