Keith Larson Messages: 34 Registered: May 2009 Location: Boston
Baron
The line output from your sound card will probably have a resistor (probably 200~470 ohms) in series with the output protecting the output a little bit. Normally an amplifiers input is really high, like 10k-47k ohms, and its flat with respect to frequency. When you hang a speaker or headphone on the output the load impedance is not constant with frequency so you get a goofy tone control. Adding two loads makes things even more interesting.