A Pristine, Compact Sound Amplifier You Build Yourself The HA-S is a Nutube-equipped DIY Headphone amp kit that will let you enjoy the highest quality audio anywhere. No soldering is required, so even if you are new to the world of DIY, you will be able to assemble the HA-S to add a warm, analog tube-driven signal boost to any sound source in no time! Build your own Headphone amplifier This DIY HA-S kit allows you to build your very own Headphone amplifier in an easy and fun way, without any soldering needed. Not only that, it provides the authentic vacuum tube sound that audiophiles know and love. Built-in Nutube Nutube is a new and revolutionary fully analog vacuum tube developed by KORG INC. and Noritake Itron Corporation. The same as a conventional vacuum tube, Nutube is constructed with an anode, grid and filament, and operates as a complete triode tube, effectively generating the response and same rich harmonic characteristics of conventional vacuum tubes in a more compact, stable and energy-efficient way. The transparent case of the HA-S delivers a glimpse into this technology; allowing the glow of the tube to be visible at all times. Energy efficiency The filament of the Nutube is powered by a DC to DC converter, which consumes less electric current and thus allows for a longer battery life than other vacuum tube equipped amplifiers. The design is so efficient that the HA-S can drive the Nutube with a line voltage of 26 V using only two A4 batteries., for a rich and authentic vacuum tube sound. Sound possibilities The HA-S has a special NFB (Negative Feedback) switch, that allows you to choose from a high fidelity clean and pristine sound, or a warmer, more harmonically rich sound as expected from a vacuum tube. When the NFB switch is OFF, the harmonics present in the Nutube (triode tube) will be amplified to create a sound rich in harmonics, warmth and textures.