Pin out for the module is as follows:
Power supply J4, from left to right:
-LO : negative power supply for the LM2876
+LO: positive power supply for the LM2876
RTN: ground power supply for the LM2876
RTN: ground power supply for the LM3886
-HI: negative power supply for the LM3886
+HI: positive power supply for the LM3886
J5 is a copy of the J4 connector, used for daisy-chaining.
J3 is the signal input connector with the power connections for the low power electronics.
Pin 1 is left, marked with a white dot next to it
Pin 1: + 12/15 Volt DC
Pin 2: mute, connect to ground for a click less mute of both outputs
Pin 3: + audio in, differential input, use this input for single ended in
Pin 4: - audio in, differential input, connect to ground for single ended in
Pin 5: Signal ground and ground for low power electronics power supply
Pin 6: - 12/15 Volt DC.
The tricky thing is that this module requires up to three different power supplies if one wants it all ... the +/- 12 to 15 VDC is
straightforward and can be optained from the filtered supply for the high powered sections through 3 legged regulators.
The LM2876 is happy with power supply voltages from +/- 20 to 30 VDC.
I used +/- 25 VDC out of an dual 18VAC transformer (rectified and filtered with two 10,000uF) caps. The LM3886 on the other hand likes to see +/- 22 to 35 VDC, all depends on how much power you want to squeeze out in a choosen impedance.
(see the National spec sheets for more info.) For my testing I used the same +/- 25 VDC as it was convenient and allows me to get close to full power output in 4 ohms. Please mount the module on a decent size heatsink if you need full power out of both chips. The ground for both chips (J4) need to be connected together for the board to work.
The gain on the woofer output is about 7.5 dB higher as the tweeter output. This is not shown in my measurements that I posted on my website. I normalized the outputs to show that the crossover frequency is at 1600 Hz. Slope is >24dB, I suspect 5th order at first sight but it could also be 6th order. Did not attempt to reverse engineer the board. The woofer output has a first order high pass installed, -3dB point is at about 50Hz. Be aware of this. All by all a nice amplfier for mini monitorsand satelites, just a matter of adjusting the sensitivities of woofer or tweeter channel.
Hope this helps