Well, I have finally upgraded my 3 stage differential phono pre with only a couple of hiccups. Blowing fuses on turn on that seems to be the result of a weird problem with the power switch and a lack of signal in the left channel. In my hast to finish I neglected to solder one of the connections from the board to the interstage transformer. My bad. In my defense, this upgrade was a little more involved than that of the SE version. Four plate loads, four FETs, replacing 10 MOSFETs in the B+ and cathode "tail" current sources, building a new higher voltage negative choke input supply and a PS mod. As to that PS mod, if you want to make a nice upgrade to your phono pre it will not cost you any money, only some of your time. It involves rewiring the PS choke as a "common mode" choke. You can refer to the Lundahl data sheet for the connections.
http://www.lundahl.se/pdfs/datash/1638.pdf
I was so impressed with the improvement that I have rewired the chokes in my line stage and my mono-blocks to good effect.
