Circuit analysis of mono audio preamp (K1803 Velleman)
U1A is a unity gain buffer, given by R5/R2. C2 is there to put the non-inverting inputs of U1A and U2A at AC ground, because the power supply isn't symmetrical: it's not a low-pass. U2A has gain of 100, given by R10/R7, i.e. 220k/2k2. If you consider the OP-amps one at a time it becomes clearer.