There have been a number of threads about classical recording in the remote section of this site (as most classical work is remote). If you do google searches for rec.audio.pro, there are tons of threads there... Otherwise read about mic placement.
Most classical guys are pretty secretive about how they get their sounds... It is a combination of high-end microphones, preamps, and conversion. In classical, less is often more. If you have to EQ or compress, you haven't done your job correctly.
In classical work, creating your soundstage is an organic process that is directly related to which microphones you use and where you put them. Stereo techniques or combinations of stereo techniques are used to get this... Because there are so many ensembles to learn about and so many different instruments to learn about, it is difficult to tell about them in one thread..
If this is something that you really
want to do, I would suggest finding an engineer near you and offer to work for them. There is no substitute for learning how to record/edit classical music on the job. In the meantime, find every book and website on stereo micing techniques you can and devour them. A good place to start is Ron Streicher's book- The New Stereo Soundbook. I bought my copy from AEA in Pasadena, CA (www.wesdooley.com