1. The capacitors go in line with the + speaker wires and the head set common gets tied directly to the radio ground.
2. The other [marcbaker suggested] way you have poor stereo separation
3. if the head set wires managed to get pulled out and shorted to ground you could burn the radio amplifier IC's out from shorting a floating voltage source to ground. The capacitors will prevent that from happening.
4. I would skip the attenuation resistors myself and go directly to the speaker + lines them selves with a 100 -300 uf 25 volt capacitor for each channel.
5. And If you think it will be to loud just use that volume control thing. I hear they are included free in the design of radios just in case someone would want a lower listening volume.
I'm going to take issue with the above
1. yes, that's another valid way of doing it. If so, you require 2 capacitors, not one.
2 Please tell us how do you come to that conclusion? Maybe you know something I don't, if so I'm interested.
3. There's a 100 Ohm in series don't forget. How many ohms is the 'short-circuit' worth please? Again I'm interested.
4. Yes, you could omit the resistors and save a few grams weight and cents cost, but the resistors prevent overloading the amplifier (if a short circuit), prevent overloading headphones if volume accidently set to max, and another subtle reason, it improves the signal / noise ratio when listening at low volume, or in other words the noise floor is more noticeable with headphones, so the attenuators push the noise floor down.
5. I agree!
PS about the "loud click". Yes there will be a click, but the 100 Ohms prevents the headphones from popping. Even if you connected the headphone to the power supply, it'd still be quieter than a drummer hears hitting a snare drum. Yes, I have tried it. Both.
To sum up, I'm suggesting:
Run a wire from L+ output, via 100 Ohms 1 Watt, to headphone socket L tag.
Run a wire from R+ output, via 100 Ohms 1 Watt, to headphone socket R tag.
Run a wire from ground to - of a capactor. + of cap to headphone socket Com tag.
the choice of capacitor value is not that critical. It's like making cake mixture, if you prefer less bass, use a lower uF value, if you want to hear the switch-on click to full decibels, then make the value large. I'd go for a 220 uF, because I like the number.