Andy said:
R1 and R2 divide the instantaneous supply voltage in half. Even the
variations in the supply are divided. C1 and C2 form a low pass
filter to smooth the ripples in the supply and average the half supply
voltage down to so low a frequency that you can't hear those ripples.
How does the feedback network work?
C6 allows less feedback at low frequencies than it does at higher
frequencies, raising the gain at low frequencies (bass boost). The
pot and switch allow adjustment of the effect ot its elimination.
R8 divides the output signal down with R7, to raise the gain at all
audible frequencies.
It eliminates the gain boost of the R7 R8 divider at very low
(inaudible) frequencies), essentially opening up the path through R8
at DC, since there will be that divided supply voltage on the output
added to everything. This is a necessity when you use a single
supply, instead of a positive and negative supply.
How does c6 & p2 work as a bass boost?
See above.
Does p1 form part of the input resistance or can i omit it if i dont
need to alter the gain?
It does lower the input impedance at full volume. C5 is backwards,
regardless. The two inputs of the opamp must match for linear
operation, so there must be the same half supply voltage on the -
input as there is on the + input so there is the half supply voltage
applied to the right end of C5.
So you can just eliminate C4 and P1 and connect your signal directly
to C5.