Power Mac G4 Cube Speakers help

The D/A conversion takes place at the speaker. Digits in, PWM audio to the speaker and earphone out. There don't appear to be analog input pins on the chip, and considering the digital nature of the Tripath amp, there wouldn't be. You'd need an external A/D converter to build an analog input amp with this chip. Tripath did make chips with an A/D on chip, but not this one.

Read up on class H digital amps to see how the output stage might work.

A switching amp like this is very efficient, 95% or better, so for 10W RMS x 2 Chan, you'd draw 20 W or 4A at 5V plus a tiny fraction lost to heat. That would only occur for a single frequency sine wave, though. Music has a peak to average power ratio of 10/1 or greater, so an averaging (analog) Ammeter would read 0.4A average if the peaks were just below clipping at 4A. If the current is limited to 500mA, then peak output is 1.25W/channel, and average music will clip at 125mW. Not all that loud.

Well some online business was selling them for that much, that doesn't mean anyone will buy them...

I did however see on ebay some people auctioning them...check this out

http://cgi.ebay.com/Apple-Mac-G4-Cube-Powermac-Original-USB-Speakers-M7963_W0QQi temZ150247453024QQihZ005QQcategoryZ80072QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

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...

I guess everyone wants a solution but no one is willing to do the work. Maybe I'll buy some and see what I can do.