Been getting a lot of questions about this, so I put together a little video showing how I use my sig overdrive (Protone Bulb Deluxe) in front of a modern/high gain amp (Mesa Dual Rec) and what it does for the sound exactly.
All the gear used and details are in the video description!
[VIDEO]http://www.youtube.com/watch?v=xE5xKkFaZdE]Mesa Dual Rectifier with a Pro Tone Bulb Deluxe Overdrive. - YouTube[/VIDEO]
It sounds really good when you use the second switch on the pedal.