the chart below shows the available products and is divided according to functions and features such as eq (2-band, 3-band, no eq), power supply (1 positive power supply, 2 positive power supplies, positive and negative power supplies), surround, and advanced switches.
since the voltage at the input terminal is a bias voltage, it is recommended to connect it to gnd via a coupling capacitor. it is also possible to leave open the unused input signal pins, but external noise, crosstalk, etc. are more likely to occur.
although it is possible to connect them together, please note the following points:
・unexpected dc current may flow between unused terminals.
・since the cutoff frequency is determined by the input impedance and the capacitance value of the coupling capacitor, connecting unused terminals together to a single coupling capacitor will increase the cutoff frequency and may reduce the noise rejection effect.
・if noise from unused pins is a problem, increase the capacitance value of the coupling capacitor connected to gnd to reduce the noise from the unused pins.
accurate capacitance value is not required, but since the hpf is formed by the coupling capacitor and the internal input resistor, the noise frequency bandwidth that can be filtered varies depending on the capacitance value to be connected.
the ground isolation input is effective in removing common mode noise superimposed on both the signal input and gnd. for example, it is effective when the same noise is on the gnd side and the signal side, such as when a signal from an external device is input via rca cables.