Micro USB to SPDIF? There must be a simple solution?

Hello, In short I have an android 4 tablet with a micro usb port - and an amplifier with a spdif in. I have plugged in my old Creative Labs USB soundblaster that did a fine job when sat between my pc and my amp but pluged into the android tablet it doesn't do a thing, the light doesn't even come on, so clearly no power is travelling through the USB. Has anyone any suggestion on how I might make what I have work, or if there is an alternative 'box' that will work instead? Or do I have to do something to my tablet to make it work?

Thanks for your help.