That does help!
I'll try change the resistors R3, R4 first, and then I'll venture into R1, R2. I'd have to test them out to see how much more I need, but 9dB should be a pretty good start.
At least I now know what to do to get more gain out of an op-amp! Considering I haven't ever designed anything with one, I call that a win on my part.
For the sake of common knowledge, the mic doesn't hit the preamp before this headphone box, so that first op-amp is the only time that mic signal gets amplified on that part of the circuit.
Microphone -> PM50 mic input -> PM50 mic output -> mixer mic input -> mixer aux output -> talkback box -> PM50 headphone input
Does the fact that there's no other amplification allow me to go a little higher with the resistors?
From what I've read, PLEASE correct me if I'm wrong, the op-amp will hit saturation and clipping will occur at any more than 80% of the voltage supply for the amp, which in this case is (I assume) 12V? So, I can increase the output up to 9.6V without hitting saturation, correct? I can measure the voltage by placing my multimeter leads across the VCC and VBIAS terminals, correct? Maybe it's not a full 12V then now that I realize that it's a single supply and it's floating (is that thinking right?)
I'm getting there... slowly, but I feel like I'm making progress!