I have a Marshall JVM 205Head with a 1960 lead cabinet.

I have quite a big pedal board but it all has to go through the effects loop because if i put any pedal in front of the amp it buzzes like mad! It does not matter what pedal it is or what guitar/cable/cab/channel i use or even if the pedal is on or off.

The buzz is more static than a humming and annoys me because i would like some pedals through the Effects loop and some in front of the amp.

I am open to any suggestions or possibilities for it, and i would be very grateful!