I apologize in advance if this is a stupid question... I use either a Digitech GSP1101 or a Rocktron Xpression in the FX loop of my tube amp heads (Eganator Rebel or Marshall Vintage Modern). I have always had a question as to using the rack FX unit's output level to control the volume of the amp. Specifically, the question is...should I adjust the rack FX unit for maximum output level, and control volume on the master volume of the amp...or should I crank the amp's MV, but control volume by turning down the output level on the rack FX unit? My original thinking was that if I increased the MV on the amp, I would be pushing the power tubes more...and that I could tame the overall volume level with the Multi-FX output level. In fact, at one point, I couldn't understand the demand for amp attenuators, given that most amps have an FX loop, and one could use a prosumer FX unit, in the amp's FX Loop, to control the output signal (and volume) to the amp's power section. Now, however, I am not so sure this is ideal. I mean, when doing this, the Multi-FX unit isn't really acting like a true attenuator. Also, even if the MV on the tube amp is set high, but the signal coming from the Multi-FX into the amp's FX Return is very low, I imagine I can't be pushing the power tubes very much at all. Is this accurate? So, I guess my real question is what is the best way to set output levels to control volume, when using a rack Multi-FX unit in a tube amps FX loop (given the tube amp has a Master Volume)? Am I compromising tone by using the output level on my Xpression or GSP1101 to control over-all volume? Thanks in advance for any and all input and guidance.