Windows 7 - Does windows 7 equalize sound output?

I have an IR RC Helicopter that is controlled by IR transmitter that plugs into the audio out jack of my mobile phone (which runs an app that produces the audio signal, that the transmitter converts).

I've recorded the audio out of the app via the line-in on my computer. I get a nice signal that I can decode into the component information used to control the helicopter.

My problem is that when I playback the signal (via the transmitter, attached to my comps headphone jack) the helicopter won't respond.

I tried re-recording the audio of my computer by looping the headphone jack out back into the line-in (not sure if this is a good idea in terms of feedback). I can then record the signal output, which is similar to the source one but fairly distorted. Does windows 7 equalize sound output or something funny, and if so can I turn this off??

Cheers!

Try the line out jack on your PC rather than the headphone jack. That may make a difference as the headphone output is compensated on most computers, where the line out is not.