This is a website I have created to help people like myself, who have discovered the wonderful capability of shooting on a DSLR like Canon 550D/T2i or 7d or 60D but have been disappointed by the audio quality on these cameras. Thanks to a veteran of the DSLR video named Dave Dougdale, I am able to custom build a simple, yet 100% efficient solution to this problem. It's a stereo splitter cable that lets you bypass your camera's built-in audio gain control.
The auto gain control software in your camera adjusts the levels of the mic based on what it
percieves as "loudness". Thus if it records one's whispering in a recording room where there is
almost no other noise, it will bring the levels all the way up so that it can record the whisper at a max volume.
On the other hand if it records in a loud, afternoon-traffic environment, it will bring the levels
much lower so that the sounds don't clip. This seems a good idea and indeed is, but only not for
professional audio where sudden level changes and especially sudden noise level changes are disturbing.
I recommend you also watch Dave Dougdale's video to the left to feel the difference.
The cable works by tricking your camera into thinking that the setting is always very noisy and thus to record at a very low noise floor. In fact it's not just the cable - it is the cable and a simple mp3 player with a dummy tone (you can get the tone here btw). The hack is making use of the fact that the camera records sound in stereo format and so 2 channels. The goal is to use one channel as the "fake" channel with a loud sound and the other one for your actual audio. Of course, this way you are only recording to one channel, but since most of the mics record mono anyway, this is not a problem because you can duplicate the mic channel in post production and get rid of the dummy tone.
I have tested it to work on Canon 550d (T2i) and I know people are using it on 7d. You can use it with virtually any type of ordinarily wired microphone with a stereo jack (NOT Stereo microphone). This includes the Rode Videomic. If you are not sure whether yours will work, drop me an email.
If you are not the do-it-yourself type of person then you can get one here.