Hi Tim,

A lot of this depends on how responsive your amp and guitar are. A good tube amp will be very sensitive to your guitar volume, but a crappy one is usually not as sensitive to your guitar tone or touch.

I've found that the best sound for me is to get the distortion level that I want from the amp with my guitar volume all the way up, then back off the guitar volume to clean up the sound a little . This way the amp will tend to respond more to my touch so that it has a little more meat when I play harder and cleans up when I play softer. But some amps just don't respond this way and you have to turn your guitar volume all the way up just to get a decent tone.

Guitar tone controls tend to be very much dependant on the quality of your guitar pickups and tone circuits in the guitar. Some guitars have a very useful tone control whereas others only sound good with the tone control all the way up. I usually turn down the tone control to roll off the high frequencies when I'm playing cleaner stuff like Jazz. But I turn the tone control all the way up when I want brighter sounding tones for country, surf music, etc. I have a guitar with P90 pickups which has a very nice control circuit. When I turn down the tone control it seems to get a more Eric Clapton-ish tone for lead sounds, so I end up using the tone control even with distorted sounds.

-- Jim