Active Crossover Circuit
Crossover circuits are of two types, active and passive. Passive crossover circuit uses passive components only and they are very simple, but they waste a considerable amount of energy and also induce distortion. Active crossovers does not have the above said draw backs and they are a better option for HiFi audio systems. Active crossovers split the incoming complex audio signal into to two bands, a low frequency out and a high frequency out. These two bands a separately amplified by two power amplifier stages, one tuned to the low frequency band and the other tuned to high frequency stage respectively (bi-amping). The cross over circuit given here uses LM833 National Semiconductors. LM833 is a dual operational amplifier especially designed for audio applications. The circuit requires four opamps and so two LM833 ICs are used here. The circuit can be divided into two parts, a high pass filter section and a low pass filter section. IC2b forms a first order Butterworth low pass filter circuitry and the low frequency out is available at its output pin (pin1). The high frequency out is available at pin 7 of IC1a. For the given components crossover frequency is 1KHz and it is according to the equation Fc = 1/(2πRC).