SW1X Audio Design™ PRE IV Performance Level 4 6V6 OPT Line Pre-Amplifier   The PRE IV is a signal output transformer (OPT) de-coupled 6V6 tube output stage based, zero negative feedback (zero NFB global or local), line pre-amplifier design. It is a further development of the PRE III power line stage pre-amplifier. The difference in … Continue reading SW1X PRE IV Line Pre-Amplifier