Hi Tlevine,

The easiest way for the proper connection when you take a standard “Y” insert cable then connect the TRS connector to the LR-16 input, and connect the Send connector to the MIC peramp output, and leave the Return connector disconnected.

If I understand correctly you want to connect your Mic preamp to the LR-16, and you also want to drive some speaker with the PAM8403 speaker amplifier?