Technically, yes. However, a headphone jack does not provide a great deal of power, so you would probably need an amplifier for the sound output to actually be audible.
In most cases, no. A stereo will generally need a 3.5mm headphone jack, a 1/4" headphone jack, a SPDIF digital output, or an optical output. However, some newer systems do have a way to be plugged in through USB, and you can also buy adapters that plug into a USB slot and provide a 3.5mm headphone jack for a speaker to plug into.
buy a headphone to rca adapter
Headphone, because audio is going OUT (mic is giong IN).
You can connect a 14 speaker jack to a home tuner stereo receiver using the RCA connector.
iHome iHMP5R 2 in 1 Stereo Speaker/Headphone System - Red help keep ouside noise out
Regular passive (non-amplified) speakers will need to be connected to a power amp (an old stereo receiver can do this). Connect the line out of the computer to the aux or tape in of the receiver, and then connect speaker cables from the receiver to each of the speakers.
iPad has a 3.5-mm stereo headphone jack so yes you can connect your earphonesInput and outputDock connector port3.5-mm stereo headphone jackBuilt-in speakerMicrophoneMicro SIM card tray (Wi-Fi + 3G model only)
The best connection for your computer's audio to your stereo would be the line out connection on the computer to the auxilary input on the stereo amplifier.
The combined headphone/boom mic, usually have two 3.5mm plugs, color coded green and pink. Plug the green one into the headphone or speaker output and the pink one into the mic socket. If the headset has a single 3 ring,(stereo) 3.5mm plug, then it is generally not compatible with computer use. You may be able to find an adapter, that converts a stereo plug to two separate plugs.
To connect one speaker to the right and left outputs of a stereo amplifier, split the input into two parts. These should go to the left and right signals. The input of the amps should be a stereo input.
Any stereo amplifier these days can connect to a speaker from the 1950's. You will just have to connect one side, left or right, to the speaker. You won't get stereo. If your receiver has the option, you should select mono output to combine the signal of both channels. Never connect the left and right speaker leads together to one speaker.
A 14 speaker jack can be connected to a stereo tuner music receiver via an RCA connector.