Headphone jacks can be used as a source for recording, but are generally not preferable to a 'line out'.

• A 'line out' is designed specifically for the purpose of taking a signal from one source and sending it to another. The impedance or strength of the signal is compatable with other stereo components. The signal is constant, and having been through a minimum of circuitry it is more pure than a headphone signal.
• The signal for a 'headphone' jack has been processed more than the line out. It is not of constant strength, being subject to the volume and tone controls. This presents special problems when using it as a source for recording.

Since the signal to your headphones is intended to 'drive' the speakers in headphones, it can be stronger than a 'line out'. Some experimentation is usually necessary to adjust the volume (and tone) correctly. There are several places to make adjustments.

• The headphone volume control. This is the source. It should be on enough to give a good signal: but start low, and make slight adjustments.
• The computer's sound-card mixer. The sound card should have a mixer, with several volume controls. Look for a master volume, or recording volume. Generally, you can find an icon for this mixer on your task bar.
• Most recording programs also have volume controls, and hopefully, vu meters so you can monitor the signal.

In any case, what you are trying to do is to get the maximum un-distorted signal at each of these controls. If all attempts fail, and your signal is distorting, try a different player. There are also 'attenuated' patch cords which reduce the signal. I got one at Radio Shack a few years back. The bottom line is that a headphone jack is less than perfect as a source for recording......however, it can be made to work.