@jwpstayman , thanks for pointing that. But I managed to talk to Andy at Backert Labs and he answered all my questions. Looks like the new Rhumbas do not do phase inversion issue, since a transformer that they use inside does it (not sure if I put it the right way, as Andy explained).
I am impressed how much time Andy took to answer my specific questions related to hum, phase inversions, tube life, volume control, etc. Andy also told mentioned about a very good upgrade path for existing users. Besides the Parasound JC2 and Jeff Rowland Capri S2, I think I will seriously consider the Rhumba as a preamp upgrade. Frankly this is probably my number one preference for now.
I am impressed how much time Andy took to answer my specific questions related to hum, phase inversions, tube life, volume control, etc. Andy also told mentioned about a very good upgrade path for existing users. Besides the Parasound JC2 and Jeff Rowland Capri S2, I think I will seriously consider the Rhumba as a preamp upgrade. Frankly this is probably my number one preference for now.