When you listen to a lot of Jazz Players you realise that a lot of them play with a fairly dark tone, this is related to most Jazz Cats using a Semi Hollowed Body guitar ( they tend to sound darker ) but they also seem to roll their treble all the way down.
Plugging straight into the power amp of your guitar amplifier will give you a similar tone without rolling off all the treble. This trick can make solid bodied guitars sounds like a hollow body guitar, cool!
You could get a separate power amp, and a speaker set and use that a your main set-up (again, a lot of Jazz Players do it that way!) but you could also modify your amp by getting another input which will allow you to plug straight into your power amp. The power amp section does not deal with any tone controls of your amp, they will no longer work when your guitar is plugged straight into the power amp. It is a great extra feat. to have this on your amp. Why do amp not come standard with this mod eh?
Using a power amp may also be a good idea for those of you who like to hear their effects without any colouration of the pre amp: You will be able to tweak you sound any way you like without hearing any extras from the pre-amp. The pre-amp is the part of the amp which creates the soul ( colour ) of the amp, the power amp is there to amplify this sound –and therefore does not add any more colour to the signal—-
Hope to catch you soon again for more guitar fire.