[gaboo]

The board has (at least) 4 layers, so this is what could discern so far:

Each jack (L and R) is driven by one 2068, but the connections are crossed, the bottom
(i.e. closest to where the PCI slot) op amp feeds the L jack.

The 1st op amp in 2068 (i.e. the one which ouputs on pin 1) is configured as a differential amp and is fed from the DAC. The 2nd op amp (output on 7) is fed from the 1st op amp. So this seems a classic bridged circuit.

There is also a transistor on each output (Q2 - Q5), but I cannot trace where two of the pins go...

Comments welcome.

 

[Glassman]

those trannies near outputs must be mutting trannies, I cannot think of any other reason for using trannies near output in fact.. regarding the analog stage, it's as you described, there's two pole active low pass filter build upon one of the dual opamp's amp, the other is just inverting unity gain amp for negative output.. maybe this is not the best implementation, because the hot signal only goes through one opamp while the cold goes through two active parts.. it's just not as symmetrical as I'd like it to be, however there's absolutely no problem with such configuration..