One of the best pre I've ever had is Nelson Pass' B1 buffer.
It is one of the most neutral yet musical, it's a pity it has no gain, but if you have a pair of suitable line transformers (i.e. an Edcor 10k:10K) you can have some gain (6db) by connecting them at the output as autotransformer.
An experiment I'll do soon...
This was my old B1, battery powered and with monster 10uf output caps:
Now I'm in love with simple tube scheme, just like Bottlehead's Quickie (this is my rebuilt Quickie, with a simple Constant Current Source implementation found here
I also did a small experiment around Quickie scheme, the Cathode Follower version (with choke):
This is really useful when you don't need gain (atm I'm using a high sensitive amplifier, so I build it), the rest is like quickie: not so transparent, but with a pleasant "tube effect".
Diy is all fun!
