EL34´s in AFD amp

[Mats A]

I got a Marshall AFD100 and i´ve recently tried it with JJ EL34L´s and the tone got kind of more scooped with a bit more treble. Feels like the sound is thinner. Can it be the JJ EL34L´s causing this or is it that the amp is made with 6550´s in it?

[johniss0001]

all i can say is check bias is in appropriate range cause frankly that auto bias is a pile of shite. the jjs may require burn in and run in time new tubes tend to sound ok but after afew hours use i think it's about 50 on jjs not sure but my chinese tubes are 100hrs on the powers before they become their best.