This is a hybrid scheme, fully developed by Mouse Electronics. The sound is based on the classical principle of "warmed up" guitar signal which is transferred to the tube part of the scheme. This means that at the beginning of the path is the transistor pumping circuit, and its output signal is overloaded by a tube. The full classical transformer powered tube 12AX7 (anode 250V DC) allows you to get exactly the "warm tube" sound without noise and interference.