Playing through something like say a typical 5W EL84 amp with two stages of pre-amplification curtesy of a 12AX7, the breakup can come early in the amp's volume range. To make an amp cleaner/later breakup I have seen videos changing preamp tubes to lower gain versions e.g. 12AY7, 12AT7 etc. My question is - what real different does this approach result in when compared to simply turning the level down on the volume control to a comparable drive amount with the original 12AX7 preamp? As yet I have not found any demo anywhere that does a clear A-B of this. To put it another way, does a lower gain preamp tube increase the amount of clean volume available before breakup or does it just change the effective clean range of the volume knob sweep?