The passive splitter (the "3.5mm Stereo Splitter cable" or Y-cable) will inevitably result in hum (whether low or high pitch or both) as it simply wires the two powered Klipsch 2.1 speaker systems together. Use an active signal splitter box instead (that is, a powered signal splitter), a relatively inexpensive device. The active splitter takes the signal and reproduces two (or more) separate, duplicate signals to two (or more) devices at the same time. Connect the input signal of choice to the active signal splitter box input. Connect one of the Klipsch 2.1 system inputs to signal box output 1, the other Klipsch 2.1 system input to signal box output 2. You won't need adapters if you use an active splitter box with 3.5mm output (aux) sockets as the Klipsch input lines are male 3.5mm jacks. All signals will be on all the time with this setup. I have this same setup and it works great!