To my knowledge the Marshall Valvestate amps are all solid state, no valves at all, a simple rule to follow is that if you can't see a tube or valve from the back side of the amp, it is a 99.9% surety that it has none. Word to the Wise, playing around in the back of amps can be hazardous to your health and has been known to cause death in laboratory test guitarists, Be safe, take your amp to a reputable shop.....................