I can't find the link right now, but I've seen sales/marketing efforts _so_ determined to include "vacuum tube" in their features list, that they designed an amplifier with only opamps and transistors in the audio stages, but a single tube as a rectifier in the power supply...

Of course, because the tube rectifies more smoothly and makes the sound more pleasant as a result. They even light up the rectifier with DC to reduce humming noise...

Indeed, even order harmonics in your power supply ripple create measurably more musicality and a higher resolution soundstage... (I hate myself for even _thinking_ that...)