OK, an amplifier is basically a pre-amp and a power amp, and since we are talking about VH & Slash, we'll say this is an all tube affair, a preamp tube like in most common amps today, a 12ax7 is 2 triodes in one tube, basically 2 complete tubes in one, each half of the tube is a "Stage", in an amp we could have many pre-amps, like a Bogner has 4, some Mesa Boogie's have 3, etc.. a preamp can be a simple 2 stage (1 tube) design or multi stage, in the preamp is where you also have your tone controls, from there your signal eventually finds it's way to the power amp, in a 100 watt Marshall this is where the 4- EL34 power tubes are, this is as far as I'm going with that, you ask about your amp setting, I'll give you an example from an amp I have that might clear this up, I have an amp that takes the signal from the guitar and goes into a 1 stage pre-amp, the only control it has is a volume, you could call it a Gain control, from there the signal goes into a 2nd pre-amp which has all the tone controls and a volume, or you could call it Master Volume 1, from there the signal to the Power Amp, but before it does it goes into another Volume control, you could say it's the Final Master, if I want to drive the Power amp into distortion, I turn the Final Master to 10, and adjust the other 2 volumes as I want, just as long as I'm feeding a fairly strong signal to the power amp the power tubes will distort, and it can be a strong clean signal or a strong dirty crunch signal, the power amp just needs a strong signal, if I turn the first 2 volumes up and the final down, the sound may be distorted but the power amp is only getting a small portion of the signal and the power amp won't distort only amplify the already distorted signal of the pre-amps. VH & Slash's sound rely on two things Tubes & Power Amp Distortion, add those together and you get Mega Volume, and that gets you the long sustain and loud, clear harmonics, if you want that at a bedroom level, you'll need a 1 watt amp cranked to 10.......................