Getting rid of charge injection click and hum sound on this switch I have designed
The pop noise you experience when changing channels is most likely due to charge injection from the switch logic.  Look at page 9 of the MAX359 datasheet for a discussion on this.  This is a characteristic of all CMOS analog switches and multiplexers, but some are better than others on this particular spec.

Not having a scope, try to isolate which section is causing the noise by listening to the hum from the speaker.  Start with shorting the input at the jack to ground.  If that doesn't improve the problem, remove IC8 (MAX359) from its socket and short pins 8, 9, 15 together which shorts both outputs to ground.  Moving on, short out the wiper of each gain pot to ground.  If you still haven't narrowed  it by now, then you need to take another look at your amplifier.  

One other thing you can do is connect your DC power supply through a capacitor into your laptop mic input and observe if there's noise on it using your laptops mic check or skype or...  Do this for both + and - supplies separately.  Be sure to use the series capacitor!!