Audio Systems: speaker noise, line level inputs, preamplifier circuit

Question
Hello,

I use my reciever phono input quite a lot to listen to music off my computer or ipod.  The problems arise when my computer or ipod changes songs, and the speaker gives off a loud deep thump, almost like a pressure wave.  Is this sound an electrical signal being amplified that my computer is putting out? or is my receiver the problem?
If you could give me any insight I would really appreciate it!  
thanks,
Jeff

ps Im work in physics, so Im fairly well rounded at whats going on electrically inside these systems

Answer
You may want to try a different input, such as a tape / cd / or AUX input. Typically, the "phono" input has a preamplifier circuit built into it because the signal from a turntable is very weak. Normal line level inputs (like the ones I named above) do not have this circuitry built into them.
Although I can't be too specific, my assumption is that there must be some sort of a "spike" that's hitting the preamp and then hitting the amp. By avoiding the preamp circuit, this should solve that issue.

I hope this helps you out!