Audison Prima ASP ASP is indispensable when installing AP8.9 bit with some OEM sources requiring: only at the initial turn-on instant: a resistive load impedance at the outputs to detect the speakers presence.In case there is no load: the source disables the outputs: usually only for the Rear section.Therefore: if during the calibration process you cannot adjust the input signal level due to lack of signal on some or all of the AP8.9 bit inputs: while installing the ASP module: when you turn on the AP8.9 bit a temporary load will be simulated; afterwards that load will automatically get disabled: fixing the issue.Thanks to ASP: there is no need to mount fixed power resistors at the source outputs; the resistors would produce heat and: in addition to that: would make the source heat up unnecessarily.