This is still a definite work in progress, but here goes anyway. When I built my DIY solid state preamp, I always intended to add a line driver stage eventually. I actually found that a balancing transformer was all I really needed, but still...I can't leave well enough alone I guess. I wanted to keep it very simple, but also at the same time to try out some different approaches than using just the typical 12Axx tube gain stages and basic power supply. I found a nice looking circuit board for the line driver itself here: Aikido Line Driver, and went with a kit from Welborne Labs for the power supply. The turret board is also from Welborne; it contains a biasing network that I wired up for the DC filament supply. The rack case came from Par-Metal, the output transformer from Jensen. So far I have been going between two 6SN7s and one 6SL7 paired with one 6SN7. I don't really need the extra gain from the 6SL7, so I'll likely settle on two 6SN7s in the long run. Initially I set the line driver up with a fairly high input impedance so I could use a passive bass directly into it, if desired. I've since decided that I prefer it with either my SS preamp or my active basses straight in, so I've optimized things for that now. I may implement a "loading" function if I find it useful in testing. I'll post some clips and updated distortion and noise specs in a few days, after I dial in a few more things. As you can see, there's plenty of room for more features too. It already sounds pretty danged good IMHO though.