Understanding Op-amps (in the context of an equalizer circuit)

[obs]

Hi All,

I've been building and modding audio electronics for several months now, but I still don't understand op amps in any great detail.  I've looked at some resources, but I can't seem to understand how to use one in a real situation.

So I was hoping to get a better understanding of op amps in general by modifying this equalizer circuit to work the way i'd like it to.

Heres the schematic, it's the "bass mid and treble eq" on the lower left.



It looks to be a variation on the tone control circuit that's in the lm833 datasheet.  My understanding of how it works, is that it is a basic inverting op amp application, with the gain of each band determined by the amount of feedback across the op-amp, which is varied by the three potentiometers. 

However, there are two aspects that I'd like to improve in the circuit; boosting the output so it is at least equal to the input (it currently gives a fairly strong attenuation), and increasing the depth of the equalization, because the changes are fairly subtle. 

I've played around with increasing the resistance of the feedback across the op amp, as I thought it would increase the gain, but I really don't know how to achieve what i'm looking for.  Any help would be appreciated!