Guitar/Tone and Volume
3 zones of distortion 
The starting point for dialing-in various electric Rock guitar tone is not a crystal-clean full-range amplifier and speaker, but rather, a tube power amp pushing a guitar speaker that has limited frequency response, with the power tubes on the edge of breakup.
With power-tube distortion, and to a lesser extent with preamp tube distortion or solid-state distortion pedals, there are three zones: Clean, Compressed, and Distorted, somewhat corresponding to the terms Clean, Crunch or Rhythm, and Lead. The Clean zone ranges from literally clean with linear response, to the beginning of warmth and some smoothing and coloration. The Compressed zone ranges from slightly warm, smoothed, and colored, into slightly audible distortion. The Distorted zone runs from slight breakup to full distortion.
Controlling distortion voicing 
An electric guitar has a volume control and tone control. The volume control almost always has a side-effect on equalization as you turn it down, affecting the pre-distortion equalization (EQ). The tone control reduces the amount of treble, affecting the pre-distortion EQ and thus the distortion voicing.
For increased control of the pre-distortion EQ, place an equalizer pedal in-between the guitar and the first distortion stage such as a distortion pedal or the guitar amp's built-in preamp. Switch between all the pickup settings, in conjunction with changing the distortion settings and EQ settings, to use the full range of basic sounds or "tones" the amp can produce.
The preamp Gain control on the distortion channel of the amp, or the Distortion control on a distortion pedal, sometimes has a side-effect of changing the equalization and thus the distortion voicing. In that case, you can use a lower distortion setting combined with a higher volume setting prior to the distortion stages, to dial-in a different distortion voicing with the same amount of distortion.
The tone stack on a standard tube amp is in-between the preamp distortion and the power-tube distortion. Thus the tone stack acts as the final part of shaping the preamp distortion voicing and also shapes the power-tube distortion voicing, together with the Master Volume control, which affects the amount of power-tube distortion voicing. For maximum power-tube distortion, set the tone controls and Master Volume to maximum, which is equivalent to bypassing them entirely.
When setting the preamp distortion, learn all the ways to adjust the equalization before the preamp distortion, including the guitar's volume and tone controls, a wah pedal, an equalization pedal, and any other volume or tone controls prior to the distortion stage. These affect the distortion voicing. More treble causes the treble to predominate in the complex clipping, resulting in a glassy liquid breakup tone; more bass prior to a distortion stage causes a dry, crusty breakup tone.
The same principles hold for controlling the power-tube distortion voicing. Learn all the ways to affect the equalization and level prior to the tube power amp, but after the preamp distortion.
Obtaining distortion independently of volume 
To get power-tube distortion quietly or independently of volume level, use a power attenuator or an amplifier that has a built-in power attenuator, or a built-in power-supply based power attenuation (Power Scaling, Power Dampening, a Sag circuit, or a Variac).
It is possible to further voice the power-tube distortion by placing a dummy load (usually a power attenuator set entirely to use its built-in dummy load), an equalizer, and then a solid-state power amp between the power tubes and the guitar speaker.
A guitar speaker is a complex dynamic filter and transducer. Line-level cabinet simulators attempt to simulate this complex dynamic sound.
In the recording studio, the amp head and speaker cabinet are typically separated and the miked speaker cabinet is placed with microphones in a soundproofed isolation booth or in the live room. Either location is a soundproofed room separate from the control room where the mic signals return and the full-range monitor speakers reside for listening to the resulting power-tube distortion sound or loud quasi-clean amp sound at a controlled volume. In a home studio, the guitar speaker is sometimes placed in an isolation box with microphones.
Place one or two microphones near the guitar speaker. If you use two microphones, this causes some complex comb filtering; be prepared to swing the mixer's equalization for the two channels around very freely, because the effects of comb filtering are unpredictable. If you use a single microphone, setting the mixer's equalization is more straightforward.
- AmpTone. Guitar amp, tone, effects placement, and cranked-amp tone at any volume
- Tons of Tones !! : Site for technical information on Amplifier Modelling