sf: the Marshall Mode 4 was conceived not to emulate/ incorporate other Marshalls, the JVM on the other hand is virtually a Marshall based on some of the manufacturer's past/ present tones, you have to hear the diff. i'm not a big fan of Marshall's tube tone, they sound fuzzy more than distorted but the JVM has something i like 8)
i'm currently playing the JVM with a drive booster which makes this amp more sizzling, very addictive too...