Master volumes were not permitted.The distortion had to come from the output stage of the amp not the over driven 12ax7's of the preamp but the 6L6's of the output stage.That came from the recording engineers not the producers.These amps were coming unhinged with the scent of burnt bridge rectifiers.An amp of 100watts rms is that is the voltage when you turn it on zero set.Peak it may do 400 watts if the amperage holds up.In the US we have alternating current.That is what fries bridge rectifiers at max op demands.To but a Marshall in the US you have to have it modified with some resistors leading into the rectifier circuits.Just a few Milli-ohms.The purpose of a Marshall Amp is for it to be cranked.it is not a jazz guitar amp.Oh man,it was so loud!No way around it though no stomp boxes,no master volume tricks,CRANKED!