For those with the Flame Boss 300, can you just use a stereo 1/8" splitter to add the extra probes? $7.99 or $9.99 for a splitter seems high. Thoughts?
The short answer is no. The probes are thermocouples and any connector must be of the correct material. In industrial settings each thermocouple has individual wiring and never paired with others. Or so it was a decade ago. If multiple probes are needed search the web for a stoker with your needs.
I suspect you could replace it with a generic splitter. It would be easy enough to try it out. You plug a probe in by itself, see what it reads. Then plug it in via using a stereo splitter, see what it reads.