Pioneer vsx-d414 home theater. No sound from subwoofer.?

[owsley'skid]

Changed the signal cable. Tried different digital 5.1 sources. Hooked up PC 5.1 sound card to the six inputs for the DVD 5.1 analog input. Only sound from the SW is when I put my ear directly in front of the front port, I hear a faint, low-pitched hum.