My tube preamp was a Van Alstine Super PAS Three. Later, I rebuilt PAS using Roy's Aikido linestage board. It sounds wonderful, but I find the same opening passage is still distorted. It isn't a big deal - a brief moment of distortion on one song out of the many I have played - but I'm curious as to what is causing it.
My suspicion is that this is a consequence of the relatively simple circuit topologies used in both of these preamps. I have in the wings Roy's recreation of the PAS4, which has a more complex topology, and I'm betting that if I ever get the cash to finish it, it will have buffers that will allow it to handle the passage without overload.