I am using the line input on my PC's soundcard (Realtek High Definition Audio) in order to use a software oscilloscope program (Visual Analyzer - www.sillanumsoft.org). I want to be sure not to damage the soundcard with too large an input voltage. I can't find any specs for this soundcard, but since it's designed to be used for audio signals, I'm thinking that I should certainly be safe to at least 1 - 2 volts p-p. Can someone with more knowledge of analog to digital conversion to a soundcard input please help me with this? Since I may want to examine a slightly higher voltage (maybe a non-audio signal), this limit is necessary for me to know. Thanks in advance. 

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I'm a stack newbie and should have researched a bit more before asking this question- I found understanding at <https://en.wikipedia.org/wiki/Line_level>. I'm using the line in, never the mic input. I'm an electronics technician, but I have no idea how to check my card's input impedance properly as Marcus suggested. I'm guessing that I'd need to choose some nominal frequency to approach measuring impedance (maybe 400hz) - but I'm used to analog mics, amps and speakers - no idea how to approach analyzing the impedance of an analog to digital input.