Designing a Line-Out Amplifier for TRS/phone connector

[MisterX]

I have a signal that comes from a computer of phone line-out and I would like to amplify or apply analog filters. I am not sure what considerations I need to make in the design. What type of load should I present to the phone? What are the signal levels? Input or output impedance? Is there a DC bias? How much power do I need to provide to the computer speakers? Are there any other considerations with stereo (unbalance) TRS connectors/cables? I would like to design a simple amplifier first.

 

[Svein]

http://nwavguy.blogspot.no/2011/02/headphone-impedance-explained.html