Re: Question about the function of overdrive pedals
An Overdrive traditionally uses some sort of clipping internally to simulate the sound of an overdriving amplifier. Generally a boost is used to push the amp into overdrive. Of course, since the first Overdrive pedals were released 40 years ago guitarists have discovered that you can use an Overdrive AS a boost, to push the amp into more clipping. Most overdrives color the sound in addition to boosting and adding gain, so this is another reason one might use an OD instead of a boost.
This usually works best when the amp is running pretty hot. A 40W amp at "bedroom" volume usually doesn't respond to using an an Overdrive as a boost like it would when it's up around 4/5 or higher. Once you get the amp turned up a bit, by balancing the output and the drive controls of your pedal, you can get a wide array of tones.