Circuit Audio processor
The
filter has 2 buffered outputs: the 2-pole output at pin 1 and 4-pole output at pin 8. Internally, the outputs are connected to 2 voltage-controlled-amplifiers (VCA).
The R15 and R16 are connected to these outputs to achieve optimum offset and control voltage suppression.
The input can be driven with source impedances up to a maximum of 200 Ω. With an input level of 0dBm, the VCA weakens by 6 dB.
The bias current needed at pin 17 is between 120 µA and 185 µA. The cutoff frequency can be shifted between 20 Hz and 20 kHz with a variable voltage at pin 5. This can be varied through P1. The capacitor values were selected to give the filter its Butterworth characteristics.
The output current of the SSM2045 IC is converted to a voltage output by the 741 opamp. Any sybsequent circuit must be DC decoupled from IC2.