in the stock form, there are no special settings to utilize this or allow you to make specific adjustments.
There may be some apps in the store that can allow you to make pseudo stereo recordings or even allow you to alter some settings, so perhaps you can ask this question in the app section, http://androidforums.com/android-applications/
, or search there to see if such discussions exist. if not, open up a thread.
There could also be 3rd party ROMs that can also allow this, and that question can be asked in the rooting subforum.
EDIT give these apps a try. I just did a super quick store search. you can also add "Stereo recording" as search words in the store and get more responses perhaps.
There may be a USB mic input on the market that can work. Again some searching is requested.