[DaveC[_2_]]

A set of desktop Harman Kardon Soundsticks are obsolete with most modern
computers. They originally took digital audio via USB output from the
computer and fed it to a multi-channel audio amplifier chip which drove 2
desktop speakers and a sit-on-the-floor subwoofer. USB drivers are no longer
available.

I'd like to make these work again by using the signal from the audio-out jack
from the computer to the appropriate points on the Soundsticks' PCB.

The main component on the PCB is the amplifier:

http://oi55.tinypic.com/egrdyg.jpg

My question is basic: how do I connect to both stereo inputs (inputs 1 and 2)
and at the same time connect to the subwoofer input (inputs 3 and 4)?

I presume the answer is a simple resistor network mixing the 2 signals for
input to 3/4?

Please be specific re. suggested connection and value of components.

Thanks,
Dave