Voltage-controlled amplifier using operational amplifier

An audio system comprising:

• multichannel limiter means for amplifying multichannel input signals by respective gains which are substantially equal and variable within a range less than or equal to a predetermined gain in response to a control signal to produce limited multichannel signals;
• power amplifier means coupled to said multichannel limiter means for amplifying said limited multichannel signals each by a substantially fixed gain greater than one to produce multichannel output signals;
• clip detector means coupled to said power amplifier means for producing a clip signal upon the occurrence of clipping in any of said multichannel output signals;
• and
• control means coupled to said clip detector means and said multichannel limiter means for producing said control signal, said control signal having a predetermined value in the absence of clipping which corresponds to said predetermined gain, said control means altering said control signal away from predetermined value according to a predetermined attack time in response to said clip signal and altering said control signal back to said predetermined value according to a predetermined decay time when said clip signal ceases;
• wherein each channel of said multichannel limiter means comprises:
• an operational amplifier having an inverting input, a noninverting input, and an output;
• a first resistor having one end connected to said inverting input and having the other end connected to receive a respective multichannel input signal;
• a second resistor connected between said inverting input and said output;
• a third resistor;
• and
• a field-effect transistor having source and drain output terminals and a gate input terminal;
• said source and drain output terminals being connected in series with said third resistor between said inverting input and said output.