A quick question , can i use a mic to amplify my acoustic instead of the quarter inch jack to get a more natural acoustic tone ? currently using my Taylor 614ce ,Shure SM57 into my Marshall AS50D but it feedsback ,squeals and pops , tried all sorts of positions .
Don't point the speakers toward the mike or you will get feedback.
You certainly can, but the SM57 is a poor choice to amplify an acoustic guitar. It is suited well for loud electric guitar amplifiers, but will likely give you less than satisfying results with an acoustic guitar.
I'd suggest you do some research on what mics are good for amplifying acoustics before you do anything.
I generally play plugged in, but have had success with a Neumann KM184 condenser microphone. Condensers require 48 volt phantom power (the Mackie M48 phantom power supply uses a 9v battery to keep everything mains-free). If an $800 microphone is out of the question, there are a great many more affordable condensers out there (including the Lewitt 140 Air which is around $150). Keep in mind that condensers are more sensitive than dynamics - and may make your feedback problems worse until you get the speaker position dialed in. They will also amplify room noise, so are generally not the best choice for a live performance situation unless the venue is very quiet. For the best plugged in tone, I use an Audio Sprockets ToneDexter preamp, which overlays a microphone image over the pickup (with a wet-dry blend). My Fishman and Baggs-equipped guitars actually sound pretty great just with the S1's ToneMatch setting, but my K&K pickups require a preamp to sound their best thru the S1.