| 摘要 |
PURPOSE: To amplify an acoustic signal without any clipping or 'bleeding' of a power amplifier by providing a voltage controlled amplifier which applies a first gain to the wide band frequency range of an acoustic signal according to a sound volume control signal, and applies a second gain to the limited frequency range of the acoustic signal according to a tone color control signal. CONSTITUTION: A sound source 20 transmits an acoustic signal to a wide band sound volume voltage controlled amplifier(VCA) 21. The signal is outputted through a low sound frequency VCA 22 and a power amplifier 23 to a speaker 24. A clip detector 25 is connected with a power amplifier 23, and the start of clipping distortion is detected. A clip signal outputted from the clip detector 254 is transmitted to a low frequency limit loop 26 and a sound volume limit loop 27. The low frequency limit loop 26 receives a low level controlled voltage limited by an operator. When clipping occurs, those level controlled voltages are reduced by the both limit loops. The limit loops provide independent activation threshold so that bleeding can not be generated by the whole acoustic signals when the voltage limiting is operated by a low frequency signal with large amplitude. |
