... I was experimenting with a mixer running through the RCA phone input (monitoring my ALC levels and adjusting settings to produce a clean signal) when it happened which I assume might have contributed to my problems. ...
There's a safe assumption <grin>
Also tells me that the problem is likely at or near the Input of the speech processor circuit.
You likely shoved a ~1.2 - 2V AC Line Level signal through a ~50milliVolt or so Mic input. That would certainly be inappropriate and could blow something active in the circuitry back to the sand from which it came.
First place to check.