O2 is a tube buffered Instruments Direct Input (D.I.) for professional use. It’s able to “oxygenize” any kind of electric and electro-acoustic instruments, like acoustic guitars and bass guitars. The O2 tube design mainly adds a second harmonic characteristic, typical of the triode in “A” class configuration. It gives emphasis on “warmth” and “thickness”. O2 has been designed around one 12AZ7A (NOS military version), improved model of the well-known 12AT7/ECC81. The gain stage works in SRPP configuration, typical in the HI-FI design. The output stage is designed around a SOWTER custom transformer mumetal shielded. O2 matches a Hi-Z input to a Lo-Z balanced output (buffer). O2 can amplify the input (+10 dB) or damp the input (-10dB), killing the noise generated by the electromagnetic fields.