Too bad this is considered information that could compromise national security...or they might've included a block diagram to inform ModelXX owners of this...The Model 12 doesn't have Aux Return inputs. To connect the return of external effects you have to free some input channel and/or use an additional mixer.
Yupp. Gotta keep the rank-n-file types from accessing such highly sensitive information about the use of Tascam gear. After all, who knows how many terrorists, agents of foreign governments, and plain cray-zee folk might be lurking on the site, ready to hold our nation hostage with secrets about routing and gain-staging and DAW control?!?The detailed answer, and the work-around, is post #14 in the "Model 12/16/24 Tips & Tricks" sticky thread. Thank goodness the OP didn't have access to the sticky threads, or try to use the search function to breech our data security protocols