Originally Posted by: RazboI kind of don't understand what's the big dif with output tubes, but I don't want to challenge that one; I'll stick to matched sets. My friend has the JC 100 watt head and put a matched set in without amp biasing. His rig sounded awesome.

If i understand correctly, it has to do with biasing your tubes. You want the voltages to be the same so that you can bias them.