So glad you are digging it!

The fact that the Pentode stage feeds the Triode stage does take a bit of getting used to but once you do, it opens up a huge range of possibilities (think guitar amp) because you can drive one into the other and leverage harmonics added at earlier stages. You can also get a wide range of tones by playing the Pentode and Triode stages "against" each other.

In terms of the air, it's currently set for just under 3db of boost but can be trimmed up or down to your taste with a set of internal trimmers. I personally like a bit less, Robert likes a bit more.

As you know, the "alt tube" switches between two sets of 12AX7s in the parallel saturation circuit, one voiced more aggressively. The "sat" knob allows you to mix in as much of the resulting saturated signal as you like but you can control the characteristics of the saturation by how hard you drive the input of the unit. This will allow you to get much more subtle results from that circuit and like almost everything else in the box, there are trimmers and adjustments that can be made internally.

Finally, the very slight physical hum is actually one of the (7) transformers. It's a good quality Hammond transformer and that slight hum is actually normal. We decouple it from the box to minimize it and although we would prefer to have it dead silent, it gives us great clean power. As you said, most people will never hear it but we could always see if we can find an alternative for you. We have gone through a lot of trouble to build the unit in a modular fashion so most parts and PCBs can be swapped or replaced without a single solder connection.

Thanks so much for taking the time to share your thoughts and let us know if you have any questions at all while you get to know your new toy!