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:QBB:I have Einstein..fantastic tones but limited features. It's not really an aggressive tone like JVM- more smooth and not as tight. It can do brutal detuned riffs with depth control turned way up but for aggressive shred lead playing the JVM is a better choice. Einstein sounds like it can't quite keep up when I'm doing the speed demon shredding. It sure has beautiful tone, though.
You definitely need to spend quality time with these amps to tweak them to their full advantage. It took me a couple of weeks with JVM to get the most I could and I am still tweaking Einstein after 8 months. These amps deserve more than a 5 minute playtime at GC, I can tell you that.