· Fully balanced input (also has separate RCA input).
· Fully balanced output (no loudspeaker terminal is connected to a ground terminal).
· Patented Dual Balanced Feedback Topology (DBFT) improves signal linearity and audio fidelity.
· Signal amplification is handled by all vacuum tubes.
· Output current amplification is handled by all solid-state MOSFET high current buffer amplifier (HCBA) output stage.
· HCBA output stage is protected for over current, DC offset and over heat.
· The S400 continuously monitors the vacuum tubes and the solid-state transistors packed HCBA. If a vacuum tube is operated outside of its allowable operation region, or any HCBA is detected with over current, high DC offset voltage or over heat, a LED lamp will turn to red. And the S400 will shut down automatically.
· Audio grade low noise toroid power transformer is used.
· Audio grade signal capacitors are used for signal coupling.
· Soft-start circuit reduces the inrush current when switching on. It also ensures that in the first 45 seconds the vacuum tubes can warm up properly. This prolongs life of all rectifying diodes, power supply filtering capacitors and vacuum tubes.