Plus, Minus, Ground and the damn noise
Now look at pins 8 and 9 of MAX359E (the switch). These lines enter on the potentiometers. The midle of the potentiometers go to the amplifier (TEA2025) and the other side of the potentiometer goes to -5V.



Why? R7 should be a volume control, right? Then the lower end should go to GND, not V-. Because your signal has positive and negative voltages.
U2 has the same problem, outer GND is tied to -5V instead of GND. This will give you serious clipping.


Please solve these two problems first. Then, you may need to have the GND tighter than 50µA, the maximum current your voltage divider R3/R4 allows. Think of an active voltage divider using e.g. an op-amp unity-gain follower behind this resistor network. Also, create the virtual GND directly from the input, then use one 7805 and one 7905 to regulate +5V and -5V separately.