Electric current magnifies circuit has a few kinds commonly usedly commonly:
The first kind: Install a resistor to do voltaic sampling below the horn namely, what actually feedback goes back still is voltage signal, it is feedback of simulative electric current, the person that do is most, but this circuit defective, , have the reason of 2 respects, the 1 output gain that is him can change as the change of impedance (horn impedance rises, output extent increases) . . . The result makes be added in the horn of 2 end is not constant voltage, , , (point to wait for an input) the power that seems to be able to make be added to the horn so is constant. . But do not forget, the sound of loudhailer presses characteristic curve is to be in what constant voltage outputs next TEST, , this kind of pure circuit is so bad sound, listen feeling not beautiful, amused just, have nevertheless improve model circuit, with voltage negative feedback is given priority to, the electric current that imposes this kind of right amount kind loses feedback, arriving is to be able to make pretty good sound, but the effect that right now electric current suffers feedback is the damp coefficient that change result puts, be opposite a frequency character impact is not big, " radio lover chrestomathy " " amplifier of high fidelity power " the detailed introduction that there is this circuit in one book. 2 it is sampling dot in the horn below, ah, the horn can be an inductance, electric current has shed inductance its are phasic can be of meeting change, low frequency is not bad, high frequency and OK move 90 degrees. . Ah, phasic and characteristic extreme difference. . .
The 2nd kind: Lose block amplifier, besides in a few special situations, what the first is used on acoustics and gain a success is YAMAHA, its main effect is pair of low frequency is outspread have very good improvement action, but the effect that can have deterioration acoustic quality however to the frequency of 200Hz above, it is to be used on sound box of ultralow frequency active commonly so. . Actually, this kind of circuit is used with sound box collocation, do not have the sense that what uses actually alone. Its job principle is: If sound box is a rigid body, so tote a pipe, with respect to the Huo Er that can become an ideal Mo Zigong cries box, , , so without giving thought to this case volume how, the degree of finish of pipe how, should accord with Huo Er only not grow resonance computation is formulary. . . . Even if the resonance of 20Hz nods what also can do to arrive, , , the size of the case, it is efficiency discretion only just, , because there is the presence of the horn on sound box, when phonating, the horn is moving, sound box is not a rigid body, so the case won't produce Huo Er not grow is resonant. . Accordingly, when if be in,phonating of the horn brace up film is fall asleep. . So, the case is close to rigid body, OK and contented Huo Er not grow syntonic condition, the OK and aleatoric resonance that designs this case is nodded. The job that horn immobile works even if negative block result puts lets when phonating. The working principle that negative block result puts is be in when the horn low frequency paragraph when working, its impedance character changes quickly, enlarge circuit passes voltaic sampling to take this kind of change feedback to give result put, , make result put the form with electric current to undertake controlling a horn, if undertake equivalent analysis to enlarge circuit, can discover result put internal resistance becomes negative block character on computation. . Make the internal resistance that the horn adds amplifier adjacent when trends magnifies at 0. . . As a result this kind of circuit makes get toward wh which direction without giving thought to in the horn very strong damp. . Should phonate only in order to end, the horn was not moved, , the case also goes rigid body. . Alleged negative block, spoken parts in an opera is make a present of of positive and negative. . Ah, know why to apply in ultralow frequency only. . . In 95 years " radio and TV " on have detailed introduction. . Can go looking
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