KORG Nu:Tekt HA-S - DIY Headphone Amplifier with Nutube, NFB, and Dual Switchable OP-AMPs

KORG Nu:Tekt HA-S - DIY Headphone Amplifier with Nutube, NFB, and Dual Switchable OP-AMPs

The KORG Nu:Tekt HA-S is a no-soldering , plug-and-play headphone amplifier kit designed for audiophiles and creators looking for a warm, analog sound in a portable form factor. At its heart is the Nutube 6P1 (all-analog triode) tube , visible through the transparent cover , which delivers tube-like dynamic response and harmonics, while maintaining very low power consumption thanks to a DC-DC filament power supply . Despite running on two AA batteries , the Nutube's line voltage is boosted to ~ 26V , delivering authentic tube character anywhere.

To tailor the tone to your needs, the HA-S features an internal NFB (Negative Feedback) switch that alternates between a clean, detailed Hi-Fi profile or a warmer, harmonic-rich tube profile . It also includes two output op-amp options —JRC’s MUSES01 (premium) and NJM4580 (industry standard)—mounted for easy swapping , so you can customize the amp’s character to your liking. With stereo mini-jack inputs and outputs , volume control , and true portability , it’s a seamless solution for enhancing listening from music players, interfaces, or laptops.

Main features

• DIY kit without soldering : assembly accessible even for first projects.
• Nutube 6P1 : Analog triode tube with harmonics and dynamics of “valve sound”.
• NFB switch (internal): high-fidelity clean mode or warm mode with greater harmonic richness.
• Dual OP-AMP included : MUSES01 (premium audio) and NJM4580 (JRC) interchangeable for sound shaping.
• Energy efficiency : DC-DC converter to power the Nutube with high voltage from 2xAA ; approx. 9 h battery life.
• Connectivity : INPUT/OUTPUT on 3.5 mm stereo minijack.
• Portable Design : 111×65×29mm and 110g (without batteries) in transparent housing.

Product benefits

• Tube sound on the move : analog character and pleasant harmonics without resorting to bulky equipment.
• True customization : adjust the “color” with NFB and switch between OP-AMPs to fine-tune response, detail, and warmth.
• Easy assembly : learn and enjoy DIY without soldering, with documentation and schematics available.
• Wide Compatibility : Output with 10 Ω and recommended load impedances ≥ 15 Ω for common headphones.

Use cases

• Portable Critical Listening : Enhanced detail and soundstage with genre-specific clean/warm profiles.
• Laptop production : Color your monitoring or reference with a tube flavor while maintaining portability.
• Home Hi-Fi : Compact complement for DACs/streamers with line output.

Frequently Asked Questions

• Do I need to solder? No. The kit is designed for solder-free assembly.
• Where do I change the NFB mode? On the internal switch (accessible by removing the cover).
• Can I use other OP-AMPs? Yes, the design allows you to swap out compatible OP-AMPs if you want to experiment.

Description for projects

KORG Nu:Tekt HA-S headphone amplifier : Nutube 6P1 tube; INPUT/OUTPUT connectivity: 3.5 mm stereo minijack; controls: volume and internal NFB switch ; output impedance: 10 Ω (recommended load ≥ 15 Ω ); power supply : 2 AA alkaline batteries ; battery life approx. 9 h ; dimensions: 111 × 65 × 29 mm; weight: 110 g (without batteries); OP-AMPS included: MUSES01 and NJM4580 ; includes manual .