It depends on whether you want to send to your Octa and/or pedal in mono or stereo. Mono is easy with lots of options; stereo a bit less flexible
For mono…
You can pre-listen to Aux 1 and Aux 2 in a number of ways—there are buttons to switch the HeadPhone 1 or 2 output to only listen to Aux 1&2 (rather than the main mix), so you can pre-listen to the Send output that way. And it’s independent for each headphone output, which means you can use HP2 as an extra send if you’re desperate for sends, while still being able to listen to the main mix on HP1).
Or you can use “Solo” to pre-listen to each track, though not necessarily what’s going to the Send. As discussed above, Aux 1 can be set to either pre- or post-fader. Aux 2 is only post-fader.
There are also AFL buttons for each AUX channel, but honestly I find their interaction with some of the other pre-listen/soloing buttons to be confusing so I tend to ignore them.
For stereo…
I don’t think you can pre-listen to the Sub outs other than hitting Solo on whatever tracks you’re sending to it, which isn’t really the same. So your only option there would be to use Aux 1 and 2 for your stereo L and R.*
*(Or, if you have a patchbay in half-normal mode, you can use that to “tap” the signal before it routes out thru the bay and listen at the patch.)
Also, keep in mind that Model 12 doesn’t have any dedicated FX returns, so unless you unplug one of your monos, by my math, you’ll be one track short to record the output of that pedal.
This thread from the Tascam forums may have all the info you need:
HOW TO SET EXTERNAL EFFECTS ON THE MODEL 12
FWIW, here’s my go-to FX SEND setup:
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SUB BUS—> Almost always goes to an EQ, a compressor, or both, then back into CHANNELS 9&10, which I tend to use as my Mixdown channel.
- OR I use SUB for resampling and have the SP404 MKII on 9 & 10. SUB BUS routes to the 404’s inputs, pretty much the same as you want to do with your Octa.
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AUX 1—> Usually goes to delay or overdrive, then gets returned back to and recorded on CHANNEL 1
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AUX 2—> Usually goes to delay or reverb, then gets returned and recored onto CHANNEL 2.
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AUX 3 (AKA Headphone 2 out)—> Occasionally I’ll use this as an extra send but it can be annoying and kludgey.
I also usually feed a bit of AUX 1 (delay or distortion) into AUX 2 (delay or reverb) for more depth. The Model 12 makes stacking effects like that pretty easy.