A little lesson here.
In order to double the volume of a 50 watt amp you would actually need a 500 watt amp. In reality sound is measured in decibals and not wattage, power is actually measured in wattage.
The reason amps are rated in wattage goes by how much wattage you need to run the amp. Examples, a 50 watt amp is called that because you need at least 50 watts of power to run it, that would be each tube requires 25 watts. Now if you have 30 watt tubes and you have two tubes then it would be a 60 watt amp because it requires 60 watts of power to run the tubes. In reality though, amps power trannys will actualy be rated higher because there is more electronics then just the tubes to run, so the tranny will usually be around 250 to 300 watts.
Now the difference between 50 watts and 100 watts is the type of distortion you like. If you like pre-amp distortion then you will want 100 to 150 watt amp because you want more headroom.
However if you prefer power amp distortion, then 50 watts will do you better because the tubes will saturate quicker at a lower volume giving you power amp distortion.
So lets go over this a little on what we have learned.
Power amp distortion is created when tubes are pushed to the point that they saturate and distort, this happens when you turn the amp up in volume. If you have two tubes they are gonna saturate at a lower volume, however if you have four tubes, you have two extra tubes (more headroom) so it will take longer for all four tubes to saturate. Power amp distortion is usually warmer and more creamy depending on the tubes.
Pre-amp distortion is just that, created by cascading gain stages in pre amp tubes. Pre amp distortion is usually a little more brittle or buzzy, but can also be warm with the right pre amp tubes.
That is why when you turn your dual up it starts to sound heavier, because not only are you having the pre amp distortion, but the power tube distortion is starting to kick in as well, so your distortion gets thicker. However alot of people hate the way power amp distortion sounds, if you are running EL34's you will get more midrange, or a honk in your sound. 6L6's are more of a scooped with nice lows and shimmering highes.
Of course there are other ways to make tubes saturate quicker, this is done by biasing the amp hot, which adds more current going to the tubes which will cause them to saturate quicker. However when tubes saturate they will die quicker, but you get a great sound, this is also the classic marshall sound.
Mesa boogie however does a cold bias because they rely more on pre amp distortion, when you turn the amp up the bias gets a little hotter creating more power amp distortion, however not as much as say a marshall has.
The reason alot of people like amps that you can bias is for the fact that they can control whether the amp runs hot or cold. However with a boogie amp you can also control this by ording tubes that draw more current which will make then run hotter, someone like bob at eurotubes will be happy to help you out with this, or when ordering from another company also express you want tubes that will run hotter in a fixed bias amp.
