Robert Wortman
100+ Head-Fier
When the Saga is at max volume it is essentially a direct connection between the source and the amp with no internal resistance. At any other setting it is both a resistor in series with the amp and a resistor in parallel to the amp. The powered off amp has an input impedance even when off. The source component's output impedance is interacting with the impedance (resistance) of the Saga's passive components combined with the impedances of the two amps. When the Saga is turned all the way up it is essentially a wire and now it's resistances are not in the circuit any more. Some investigation with a test signal and an oscilloscope would be interesting. Any distortion that is clearly audible should appear on the scope. When the Saga is in active mode, the source component only drives the input of the active buffer and the Saga is driving the impedances of the two amps.