SW1X Audio Design™ PRE V Performance Level 5 71A/45 OPT DHT Line Pre-Amplifier   The PRE V is a signal output transformer (OPT) de-coupled 71A/45 tube output stage based, zero negative feedback (zero NFB global or local), line pre-amplifier design. The DHT tube output stage is similar to the output stage as found in our … Continue reading SW1X PRE V DHT Line Pre-Amplifier