Help me understand reference voltages!

[sfr]

Okay, my knowledge of how these circuits work is very very spotty.  I'm still filling in the blanks as I go along. I'm probably using the wrong terminology everywhere.  Feel free to correct me, but please bear with me!

I'm working on laying out the metal zone style EQ on a PCB.  I breadboarded it forever ago and had it working.  (Referencing Michael Burgandy's schematic here)

Since I'm liable to have half a dual op-amp left, I figured maybe I could tack a microamp-style circuit on the end of it.  (Referencing the tonepad layout here)

The VRef for the EQ comes off the middle of two 10k resistors between V+ and ground, with a 100µf cap between the Vref line and ground. 

The microamp has Vref pulled out of the middle of two 100K resistors, with a 1µf cap to ground.  Between the various circuits, Vref is fed through different resistors as it goes into the non-inverting input of the op-amps.

Now, as I understand it, this is sort of to bias the opamp?  Adjust the gain?   That's the reason that the voltage divider and the resistor coming out of it are different between the Microamp and Dist+?  (My Dist+ makes some distortion even w/o the clipping diodes - I'm assuming the thing is trying to amplify more than it has power for, resulting in some clipping as it runs out of headroom?)

So to tack the two circuits together, and get Vref from the same place, I need to calculate what voltage would normally be, and work around that?  So if I used the Vref from the EQ schematic, I would cut out the divider from the Microamp schematic, and alter R2 (coming off my new Vref line) so that the voltage coming out of it is what is expected in the circuit?  If this doesn't work, I may need to calculate new values all around to make all the expected voltages work?

So my sort of really really vague understanding here - is it even remotely correct? 

I assume I need to start reading more about opamps so I understand this stuff more - can anyone recommend a book or website with good basic info?  I need to learn how to calculate these things.