I just found this thread. Appreciate NoPants subjective impressions. If I was to design/build a Megatron-type amp I would probably use different front end tubes, like a 6SL7 for the input diff amp/LTP and 6SN7 for the driver tube. To me, the advantage of a high gain tube in the first stage is it makes the gain similar for the two phases regardless of whether it is driven balanced or unbalanced. Since my system is single-ended that makes a difference. The 6SN7 is a better driver tube than a 12AX7, which is kinda wimpy. Furthermore the 6SL7 and 6SN7 are more linear than their 12AX7/12AU7 counterparts. Not sure why Kevin decided to do 12AU7 for the input and 12AX7 for the driver rather than the other way around, although to be fair, the Jadis power amps use a similar input topology with the same tubes in the same order and have a good reputation for sonics. If I had to guess, I would think that the reason for using the 12AU7 first is to keep the gain between the two phases close, since there is no overall feedback to the first stage. There is overall feedback between the second stage and the output stage, and the 12AX7 provides high overall gain to allow the closed loop gain to be identical (within the tolerance of the feedback resistors) between phases. I also agree with Frank that I'd use solid-state current sources, e.g. cascoded MOSFETs for the output current loads as they are much closer to the ideal constant current than a single EL34 power tube. However, that would mean there would have to be some additional circuitry to adjust the balance and output voltages, whereas with the Megatron because the top and bottom are identical there is a self-balancing to keep the output voltage near zero.