Was all Tom's doing. I didn't know he was going to do it until it was done
Little adjustments keep reducing it little by little. We prototyped some different PTs that reduced one type of hum, but due to weird core saturation issues, caused a different kind. I have yet another proto sitting here waiting to be tested which I might get to this week.
But, the hum is really pretty low. I am alarmist about such things as my test is generally that if I can tell an amp is on, it is too noisy. The Torpedo is to the point where on a very quiet night with no heater/ac/road/tv/etc. noise, you can just tell it is on ... depending on the sensitivity of the headphones. So, the hum is low enough for a $300 amp, but probably not a $2000 one.