Wayne Parham Messages: 18791 Registered: January 2001
Illuminati (33rd Degree)
It's a reactive network, and the only real difference is that the output level filter is designed for a low impedance load whereas the input level filter is designed for a high impedance load. As an example, a filter designed for the output circuit might use a 10µF capacitor, having reactive impedance of 8 ohms at 2kHz. With an 8 ohm speaker load, that's an appropriate value. If the preamp input impedance is the typical 47Kohms, then a similar preamp-level filter might use a 1700pF capacitor instead. But the basic filter is the same, just using different values that are appropriate for the impedance of the circuit.