相關(guān)元件pdf下載：bc109c lm380 bd131 
the soft switching is enabled by a bd131 transist wired as a switch in emitter follower configuration. the collect is wired to a permanent supply voltage, the 2h series induct serves only to filter out power supply hum. this induct is not too imptant may be omitted if the dc supply is adequately smoothed. the control voltage is applied to the bd131 base terminal, the 10u capacit 10k resist having a dual purpose:-i) a gradual ge of the 10u capacit ensures that the transist will switch linearly from 0 volts to full supply, ii) serves as a hum filter ensuring a very smooth dc supply to the amplifier tone controls.led1 will light when the amplifier is on. the control voltage should ideally be 0 volts when the amplifier is off full supply voltage when on. the lm380 is shown driving two 8 ohm loupspeakers, the load is therefe 4 ohms. the 4u7 capacit acts as a crude crossover, lower frequencies are impeded so this loudspeaker may be a "tweeter" type.
