This project utilizes the connection between common base and common emitter circuits. The transistor Q1 is connected as a common base amplifier and has a low input impedance and high output one. Q2 is emitter follower with high input and a low output impedance. Both circuits have a 0 deg phase shift, so no Miller effect is present. All these, make the pair easy to couple and with high frequency range.
Semiconductor 19: Common Emitter Mode of Transistor - Tronnixx in Stock - http://www.amazon.com/dp/B015MQEF2K - http://audio.tronnixx.com/uncategorized/semiconductor-19-common-emitter-mode-of-transistor/