Split monitoring FAIL

[Toast]

Okay, so like lots of aspiring home studio aficionados, I've essentially maxed out my channels and am experimenting with alternate solutions to opening some more up (rather than accumulating more hardware). I ran into an issue last night. I'm pretty sure I know what the issue is, but I don't know WHY it's an issue. Maybe someone here can help me out?

So, split monitoring. I have a Mackie 1604VLZ Pro mixing board. The simple idea is you plug instruments/mics into channels 1-8, direct output those into tracks 1-8 of the DAW, output the DAW back into the mixer's channels 9-16. Don't assign output of the mixer's channels 1-8 (don't send them out to the mains (L-R) or the subs (1-2, 3-4)). Assign the output of channels 9-16 instead, and you can now monitor the DAW's output without affecting the signal being recorded (mixer 1-8 out to the DAW). 

But my DAW has mic preamps on tracks 1-4. So I thought I could save myself four channels on my mixer. Essentially: vocal mic straight into the DAW's track 1, outputted to mixer channel 9. Second mic straight into DAW's track 2, outputted to mixer channel 10. Two more instruments straight into DAW's tracks 3 and 4, outputted to mixer channels 11 and 12. THEN ... instrument into mixer channel 1, out to DAW track 5, DAW out to mixer channel 13. Another instrument into mixer channel 2, out to DAW track 6, DAW out to mixer channel 14. And on down the line. 

So ignore DAW tracks 2-4 for a moment. DAW track 1 is successfully outputting to mixer channel 9. HOWEVER, although DAW track 5 is supposed to be outputting to mixer channel 13, it is INSTEAD outputting into mixer channel 9 just like DAW track 1's output. So is DAW track 6, which should be outputting to mixer channel 14. And on down the line.

Why do DAW tracks 5-8 output to the same mixer channel as DAW track 1, even though DAW outputs 5-8 are sent to mixer channels 13-16?

I don't think it matters, but DAW tracks 1 and 2 are condenser mics taking phantom power from the DAW. They're the only tracks receiving phantom power.

 

(P.S. I'm experimenting with a second alternate solution to making more tracks available which I may post in a new thread if/when this output issue is figured out.)