The voltage follower Q2 bootstraps R5 to give it a greatly increased
apparent resistance which both increases gain and reduces distortion.
Q1 is biased through R7 and R8. The voltage at the emitter of Q1
follows that at the input C2 therefore C2 bootstraps R8 and greatly
increases its apparent resistance and also stops undesirable negative
feedback through R7 and R8. R6 by itself increases the input
impedance somewhat and improves linearity. Negative feedback from the
collector of Q2 controls the gain of the circuit and improves the input
impedance still further. The overall gain can be controlled by
Some further improvement can be obtained by replacing the PNP
emitter follower by a complimentary feedback pair (CFP) follower.