First of all, tried searching, but couldn't find the simple explanation I was looking for. So: what does a preamp pedal (like this Electronix "Submarine" I was looking at on ebay) really do? How does it affect the sound, as compared to playing straight in, no effects? Sorry for the newbie question, but I guess that's what I am. Thanks in advance -
The word "preamp" gets used a wide range of ways. The two "key" elements (which are not always together in the same unit) are tone shaping and gain boost. In the case of the Submarine it's a subtle amount of tone shaping combined with a moderate amount of available gain. Remember that gain just means increasing the signal level, it doesn't mean distortion unless you're boosting the signal level into a device that's designed to distort. So the main thing to know is that there is no one way that preamps "sound" or affect your sound- they are all different. And there is no one amount of gain or type of output signal- they are all different. You really have to take them on a case-by-case basis and ask "what does this specific pedal 'do' and 'sound like'?"
The preamp in the HBE Hematoma can be used as a clean boost that adds a ton of punch. I really like it.
To clarify my earlier post a bit too, it's in the nature of amplification circuits that they will probably color and/or compress the signal a bit, even when the desired tone is supposed to be "clean". Basically any time you add components, they may alter the signal. It is possible to design for the least amount of coloration or the least amount of compression, but it is also possible to consciously choose amplification designs which are known (or discovered) to offer musically pleasing alterations, even while sounding like there is no "effect". When people say their amp sounds really "natural" or "smooth" or "clean but not sterile" they are saying there is a subtle coloration which improves the signal in a musical way without being an exaggerated effect; and when people say a certain amp is "punchy" very often that means there is a slight amount of compression, just enough to seem punchy but not so much that it "sounds compressed". Again, this happens even if there is no "compressor" built in to the amp; it's just a part of how some amplification stages affect the signal. And that, generally speaking, is what preamp pedals do.