Schematic by Bruce Rozenbilt (Glass Audio 1991)
It amazing how few components are needed to build this pre amp. The theory of how and why it works is in Bruce Rozenbilt”s book BEGINNER'S GUIDE TO TUBE AUIDO DESIGN. Another good source of information about the µ follower is Morgan Jones’Valve Amplifiers.
The valve circuit is a common cathode amplifier, but with an active load. The upper valve is a constant current source or active load and the lower valve is the cathode follower. The advantage of this pre amp aside from its simplicity is its low distortion. If you’re looking to minimize the components in your signal path this amp is definitely a candidate.
In my version of it I didn't use the tape monitoring input or output jacks.