Electronic – Capture Analog Audio Output from a two-way radio

Given the vastly changed info... TDA2822 is a low power chip (under a 1W; its datasheet recommends it for "portable cassette players"), and of course the speaker it sends to is only 2.5W (doesn't get that much). Basically you can take the output of this amp (from the speakers' wires) straight to any professional line in audio equipment. It's like plugging in a walkman. No divider or anything like that is needed. Professional equipment accepts "hotter" signals than the consumer ones; see line level. Check with a voltmeter just in case that you don't get way over (say no more than 2V RMS on whatever it blasts the loudest), but there's not much else to do.

Also the quality of the PCB isn't great... but do you want NASA standards in toy using a $0.10 chip? The last image are "mouse bites", but those are normal.

Regarding the power supply info (added in a comment): 7.5V is how they get this chip to make enough sound for a loudspeaker. Likely the TDA2822 output doesn't get to the rails (i.e. it's less than 7.5V peak); most amps can't swing all the way to the rails, typically they can go up to 1V or 2V under. Some of the more dinky mixing consoles I've seen the innards of have only 6.3V rated caps on inputs; that mixing console was powered from 6V. So... there's potential danger of damaging a mixing console over a long period of time if this toy outputs to its max volume; we're not talking about immediate fireworks. If the mixing console is powered by more than 6V supply chances are good it uses higher-rated caps on inputs so the danger of damage becomes practically nil. If the mixing console is a profi one it will have maximum input level somewhere in its (service) manual. For example, a TASCAM I have specifies maximum input level as +18dBv (8 V).

Getting a little off the question here but I think we have an XY problem situation here.

Going by the comments you don't need to get 4 analog signals into the audio input of a PC.
What you need to do is get 4 analog signals into a PC/phone as cheaply as possible.

That is a very different problem.

For the price of a 4 input analog multiplexer and the electronics to switch between the inputs at the appropriate rate you could probably get a small micro controller with 4 analog inputs. This would allow you to sample all 4 signals constantly at a sufficient rate and then transfer that data to the PC/phone over USB. It has the added advantage that unlike the microphone socket the USB socket would also be able to supply plenty of power to run the external electronics.