I have an MG50FX amplifier that is less than half a year old and in the middle of playing the distortion will fade to the point of disappearing and will then suddenly come back in the middle of a note. What could be causing this?

Normally that would be caused by a dirty footswitch jack or a broken (intermittant) cable on the footswitch itself. If neither of these is the problem, it will be a relay in the amp and will have to go in for service. Here's a link

http://www.marshallusa.com/service.asp

For aproblem of this nature, I would suggest contacting Korg directly. Here is a link to their contact page. Contact KORG

I'm not sure which amp you're playing thru. but generally the settings you want for a clean sound. check your drive (or Gain ) knob. You want it about half way.and your Channel volume, half way. those are good starts. then let your master volume do the rest. Also, make sure, if you have active pick-ups on your guitar. check the batteries. if they're low, it can cause distortion. if this doesn't resolve, then its internal. could be anything at that point.

try using less compression

sounds like out put transister
or power overload

Using the CORRECT footswitch for this model, you just plug it into the footswitch jack. You MUST use the correct one for the model.

Try this site... you MIGHT have to register, but it is free.

http://www.retrevo.com/support/Marshall-MG50FX-Amps-manual/id/23592ag624/t/2/

Usualy bad solderr joints on the output pcb

have you got valves fitted to the amp as they can cause fading if old >damaged >not fittted properly also check the speaker connects and try playing half volume the output should be steady.. you say its handmade if you made it pull out the amp board and check your soldering joints look to see fi there is any that need resoldering as they may be getting hot and causing a resistor to fade..