Okay. Makes sense.
I found the model of the the tripath chip used. It's the TA1101. The weird thing is that a few websites spec this chip as running on 12V.
http://eetimes.com/news/98/1011news/introduces.html
I found a "data sheet" here:
http://www.htmldatasheet.com/tripath/ta1101b.htm
and this evaluation board?
http://www.elatec.cz/tripath/pdf/EB_TA1101B.pdf
Now I don't know if the TA1101 for the cube was a special of version or not, but it can't be much different.
By the way, how do we know that the conversion takes place at the speakers? How can that be possible? I thought speakers can't produce anything other than analog sound.
Some things I found according to the data sheet:
@ 10 W the chip has 88% efficiency. That's pretty good.
On the pinout, pins 3 & 8 take Digital/Analog 5 volts. USB provides digital 5V. I'm wondering what the analog is? But pin 27 says Analog 12V. I wonder what that's for? Can you power the chip with an external 12 V PSU?
Page 5 pinout definitely shows an input of 12V. Where does the chip get 12V from if it's running off of a USB port which only provides 5V? Also, if you look at the speaker connections at the top right of the chip and follow them back to the chips leads, it looks like sound outputs P & M come off of pins 25, 23 and 20, 22. Could those not be the line level signals we are looking for? It seems like after those outputs, there's just a bunch of capacitors right? I don't see where the conversion from digital to analog takes place. And I don't see how it can be post-amp speaker output.
If feel like buying some and trying this myself...