I connected my audio amplifier to laptop's headphone socket and got oscillations which came and went away according to hand capacitance. Does anyone have any idea what's going on please? The AX-M66 has four coaxial input sockets marked L (red), L (white), R (red), R (white). All the screens are commoned. Which pair of connections should I be using? I've connected L(red) and L (white) and the common screen to the 2 core screened wire going to the laptop. Is this correct? Why might the setup oscillate, making a sort of scratching sound?