When I switch my Marshall MG50FX amp on the sound is very soft even tho the volume is on max. when I switch on the gains control and turn the gains control switch I have more volume, but a buzzing noise. please help.

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

"Overdrive Channel: high frequency noise as the gain and volume are increased."

This is the expected result, you are experiencing feedback. Try turning the "Contour" knob all the way to the left and turn down the tone knob on your guitar.

This amp has a design defect in the TDA7290 power circuit board. The heat sink is too close to main board when installed (at 90 degree angle) and can TOUCH the power signal on the board shorting out the fuse and/or transistor. I bent back the heat sink bracket slightly and it powered on fine. Also, the cooling fan must be 100% flowing or the transistor will cook in a short time, replace it also with new transistors (its a 5v computer chip fan). Good luck from Arlington guitar shop dot com.

The Marshall is a super clean acoustic amp.

The POD is overloading the amp.

Try the electric guitar input and keep the gain on the amp down, keep the EQ level and use the POD and the end volume to adjust the final volume.

The normal inputs is for a low output acoustic pickup - the POD is a high output electronic source.

Start with the Marshall gains low and get the clean sound good, then work on the gritty sound.

The amp is voiced for a sweet clean sound - if you want grit'n'ball change to a 50w Marshall valve head and a 4 X 12 cabinet.

Horses for courses

This usually indicates that your neutral and live are backwards. Try plugging the unit into a different outlet elsewhere (different room)
If it still is buzzing, look for a GOUND LIFT switch in the back, it may have inadvertantly gotten flipped to the wrong position.

Sounds like one of the tubes needs to be replaced.

I may be missing something but i cant see what amp you have? Is it a valve or solid state marshall?

There are many models of Marshal amps icluding 15Watt types.

First thing to try is to see if headphones have normal volume. If they do, then the headphone jack switch that connects the speaker is LIKELY bad.

If the headphones do not have any volume, LIKELY causes are:

1. Fried output power amp

2. Volume pot is broken or has bad solder joints to the circuit board.

Make sure the master volume is turned up and the inout gain is down some.

All of the electronic devices suffer from the statistical noise within the amplifying components. Keeping the inour gain down some tends to limit the gain where the hiss is most sensitive, that is the high gain in the "front end" or preamp section.

A "ton" is not a MEANINGFUL measure of the loudness of the hiss.

A meaningful measurement would be the Db relative to the normal program material.

Test with no devices plugged into it as the preamps in guitars can create hiss too. The hiss should be barely perceptable at 5 feet from the amp.

I can say with a fair amount of certanty that this is the control knob on your guitar, these are fairly cheap and if you have any mechanical ability you can replace it yourself, there will be some soldering involved so if you can't do that I would take it to your local music store and most have some sort of repair department, this shouldn't be a big bill to get fixed.