While there are many types of power tubes, historically, the power tubes in Dino amps are most commonly one of two types. The British voiced EL34 or the American voiced 6L6GC. These power tubes what produces that holy grail tone. Each has their supporters and detractors. Near Dino warfare has occurred over the use of these tubes. If your a diehard Marshall fan your going to side with the EL34 crowd, even though this is not the only power amp tube Mashall has used. If your a Mesa Boogie fan you'll probably end up on the side of the 6L6GC, though Mesa too has used both tubes in different models and on occasion have used both tubes in tandem to achieve a desired tone. If you would have asked my opinion one or two years ago I would have sided with the British EL34 contingent, but, during the interim I've found a 6L6GC that is just killer. Just to mess things up a bit more, my favorite tube is the EL84. I wish to hell it had more power on tap because in my opinion it produces a better high gain lead tone than either of it's bigger brothers. The EL84 is my personal tube of choice for my own signature Dino tone. But, if you want enough power for a 50 or 100 watt tube amp you'll probably pick between the EL34 and the 6L6GC. There are other wonderful tubes out there, like the KT77 which is almost a perfect mix of EL34 and 6L6GC tone, but, the mainstream amp manufacturers most often use the EL34 or the 6L6GC. If you prefer smooth look into an amp with 6L6GCs. If you prefer the classic crunchy sound of Marshall, Laney, Orange and Hiwatt, the EL34 has your name written all over it.