I use a Modwright LS 36.5 with my Baron, which works very well. Before that, an Audio Research LS-15, which also worked well. Never tried a passive.
btw, if yours doesn't have the tri-tube mod, you should get it. The Baron really sings with EL-34 tubes, although the higher bias is problematic. The original 5881's, not so much.
btw, if yours doesn't have the tri-tube mod, you should get it. The Baron really sings with EL-34 tubes, although the higher bias is problematic. The original 5881's, not so much.