Well your statment is part true, yes it does not truly bring the output power down by half, but it brings down the headroom by half and that is also what is important.
Taking out of the equastion, pedels, pickups and guitars, a tube amp tone is determined by 3 things.
So lets go over the 3 parts that makes a cranked tube amp sound great.
1- Preamp distortion, this of course has nothing to do with volume at all, it is the same wether you have the volume set at 1, or if you have it set at 10. The only thing that will make preamp distortion distort more is by throwing a boost in front of it. Reason you adjust your preamp knobs at different volumes, if you crank and amp you are going to get more bass and more treble, actualy your ears just get to a point where they hear sounds different at higher volumes and ear fatigue comes into play.
2- Power amp distortion. This is what made old marshall's sound great, cranking the power amp, it is a warmer distortion then preamp distortion. The mix of good preamp distortion and power amp distortion is what makes mesa's sound great at higher volumes, more distortion of course this way and why you can turn down your preamp gain when cranked!
3- Air movement, the speakers going back and forth, of course this is only if you are standing in front of it without a PA system. Because honestly a MIC does not really get effected by the air movement, as long as there is enough movement for the MIC to pick up the waves it is happy, it will not sound better with more movement when going into a PA system, because you can just boost that signal at the board.
So how does this effect pulling two tubes, well when you do that there is less headroom, which means those power amp tubes will distort alot quicker and at lower volumes, so you will get both he power amp and premap distortion at a lower volume and be happier. Of course if you are not mic'ing you will be getting less speaker movement and that you can feel, mostly the bass pounding.
The hot plate works almost the same, basically the amp with all four tubes will output a certain DB to that speaker cable, the hotplate takes that signal and cuts it down by whichever DB you select, there for giving you the same effect and pulling two tubes.
Like with pulling tubes you will loose air movement. Little trick with the hotplates, best to set it with about a 4DB drop, 8DB at max. With these settings the Tone is only very slighty effected and you can adjust by using the switches on the hotplate or just changing the EQ on your amp. Mostly using a hot plate will effect your treble and bass and that is why the Hotplate gives you a treble and bass booster.
And yes you can use a hotplate with two tubes pulled. If you have a 8 ohm cab, use a 8 ohm hotplate, on the back of your amp make sure to use a 4 ohm tap. Once again you will be loosing the air movement the most.
Differences between pulling two tubes and Hotplate.
Pulling two tubes you are only wearing out two tubes intead of four. People say that a 50 watt amp does not have as much umph (bass) as a 100 watt amp. But hell mesa's have enough bass already if you ask me.
Hotplate- You have to crank the amp even higher then if you were to have only two power tubes. Example, with two power tubes you have output at 12 oclock and those power amp tubes start distorting, where with four tubes you have to crank the output to 3 or 4 oclock to get the output tubes to distort. They say with a hotplate you loose some bass and treble response, but like i said you have the switches to make up for it, plus mesa's have enough bass already.
Honestly, both ways are a great way to get close to the cranked tone in your bedroom with out shaking your neighbors out of there beds. But for me if I cant crank it in my apartment, i just plug right into my POD 2.0 and get great tone too! People can put down the pods all they want, but for bedroom jams they are the ****! Notice i said POD 2.0's, to my ears they sound alot better then the newer ones.
As to the 20/20 amps, great amps, however like you said you loose the air movement plus they have less bass then a EL34, but they are sweet when they distort if you want that rock vibe, but not good for metal.
disassembled said:
Logically one would think that if you pull half of the tubes you get half of the volume output. This is not the case as it only drops the volume about 3db's. It really doesn't matter if you do it or not but be sure to match your impedance up properly as it changes when you remove tubes. The impedance on the amp gets reduced by 1 notch (ie if you use an 8 ohm cab plug it into the 4 ohm output.). To get half of the volume you would have to be running around 10 watts.
The preamp is where most of your tone is generated so if the tone sounds bad at low volumes it's your preamp settings which must change to compensate for not having loud volume. So maybe an EQ in the loop would do some good for low level practicing.
I think my TA and 20/20 sound pretty weak at low volumes(due to the speakers not being driven) but still retain the same tone as when I turn it up so I found a nice compromise between bedroom and rock and roll volumes.
Even my little 5 watt Valve Jr tube amp is too loud to crank in the bedroom. You would need a .5 watt amp if you wanted an amp to crank in your bedroom without disturbing the people in other rooms. The little 5 watt amp will give me great power amp distortion at much lower levels but it is nowhere near bedroom/night time levels.
Some other solutions are getting a little practice amp (like the boss cube or vox DA5) that will just amplify your guitar enough for practicing purposes. I think it's a waste to be running a 100watt tube amp for night time practice because you are just wearing down your power tubes more and more. A little solid state amp won't break the bank and won't sound like the pits for jammin by yourself.
Oh and I have been hearing from a lot of folks that the JSX really doesn't cut it when cranked. It's a shame about the JSX but I thought my 5150 sounded great when it was opened up and the same was true for my friend's old Ultra Plus head.
Greg
