The Nunchaku uses two Raytheon JAN6418 directly heated miniature vacuum tubes, which are especially well suited to portable audio devices thanks to their compact size, low power consumption and stable operation. The device applies a 22.5 V anode voltage to the tubes, providing greater headroom than the 9 V or 12 V solutions more commonly found in portable products.

The higher anode voltage is not just a technical detail: it gives the vacuum tube stage more operating headroom, allowing the tubes to perform with a more natural and fuller character. As a result, TUBE mode delivers a warmer tone, smoother treble and a more relaxed, analog-like musical feel, while the Nunchaku continues to function as a modern high-resolution USB DAC.

TUBE mode uses real vacuum tubes, so the Nunchaku behaves differently from fully solid-state portable DACs. Due to the sensitive structure of the tubes, a soft ringing sound may be heard if the chassis is tapped while playback is paused. This is not a malfunction, but a natural microphonic effect associated with vacuum tube construction.

When connected to a phone, minor interference may occasionally occur in TUBE mode, although these noises usually do not become distracting during music playback. In Class AB mode, the tube-related microphonic effect does not occur, the background is quieter, and operation is more stable with a cleaner character.

The Nunchaku offers two selectable output modes and, with them, two distinct sound characters. In TUBE mode, the vacuum tube stage delivers a softer, sweeter and warmer sound that can reduce the sterile feel of digital sources and create a more natural musical texture. This mode especially highlights the strengths of the tube character with vocals, acoustic instruments and atmospheric recordings.

In Class AB mode, the Nunchaku provides a cleaner, more direct and more dynamic presentation. This solid-state output stage delivers a greater sense of resolution, tighter control and quieter operation, without the natural microphonic characteristic of vacuum tube operation. Switching between the two modes does more than subtly adjust the sound, it provides a fundamentally different musical character.

The Nunchaku’s amplifier stage is not based on a simple single-chip headphone amplifier solution. The device uses two Raytheon vacuum tubes, four high-performance dual OPAMPs and four BUF634A buffer units. This type of architecture is known from high-end portable audio players, where discrete amplifier elements allow more precise signal handling, greater current delivery and more stable headphone driving capability.

The role of the buffer stages is to provide the load handling and control required for headphone driving, while the OPAMP stage is responsible for signal-processing precision. This construction is especially important with higher-sensitivity IEMs and more demanding headphones, because a stable amplifier stage results in cleaner dynamics and better channel control.

At the digital heart of the Nunchaku are dual Cirrus Logic CS43198 DAC chips. This DAC solution is designed for high-resolution PCM and native DSD playback, enabling the device to support 32-bit / 768 kHz PCM and native DSD512. The purpose of the dual DAC design is more accurate channel handling, a better signal-to-noise ratio and cleaner digital-to-analog conversion.

The low noise floor and strong dynamic range of the CS43198 chip are especially important in a portable DAC/AMP, as the source is often a smartphone, tablet or laptop. The Nunchaku receives the digital signal via USB-C, then converts it into a headphone-optimized analog output through its dedicated DAC and amplifier stages. This architecture is significantly more refined than a conventional phone adapter or basic USB audio dongle.

The Nunchaku delivers outstanding performance in the compact USB DAC dongle category. From the 4.4 mm balanced output, it provides up to 525 mW at 32 ohms in TUBE mode, while 450 mW is available under the same load in Class AB mode. This level of power provides sufficient headroom for sensitive IEMs, higher-dynamic-range earphones and many portable headphones.

The 3.5 mm single-ended output also offers serious everyday value. It delivers 125 mW in Class AB mode and 150 mW in TUBE mode at 32 ohms, so the Nunchaku is not limited to balanced systems. The low gain and high gain output voltages allow more precise matching with both sensitive and more demanding headphones, while maintaining a wide usable power range.

In TUBE mode, the Nunchaku has a warmer, smoother and more analog-like sound character. The bass region feels fuller, the midrange more natural, and the treble appears with softer contours. This tuning is not about sterile detail retrieval, but about a more fluid and musical presentation, where the vacuum tube stage gives the sound a subtly more relaxed texture.

In Class AB mode, the Nunchaku offers a more precise and tighter presentation. Dynamics are more immediate, spatial imaging is more defined, and details separate more clearly from the background. The 4.4 mm balanced Class AB output provides a quiet, high-resolution background with its 130 dB signal-to-noise ratio and 130 dB dynamic range, while TUBE mode, with its 107 dB signal-to-noise ratio and 110 dB dynamic range, places greater emphasis on vacuum tube character and a more organic presentation.

The Nunchaku offers two types of headphone output: a 4.4 mm balanced connection and a 3.5 mm single-ended connection. The 4.4 mm output provides higher power, better channel separation and wider dynamic headroom, so the device’s full capability is best realized with a balanced headphone or earphone cable.

The 3.5 mm output provides a more universal connection option, allowing the Nunchaku to be used with conventional headphones and IEMs as well. Both outputs offer a frequency response of 15 Hz to 40 kHz, providing bandwidth beyond the audible range.

In TUBE mode, the Nunchaku uses JRC hardware volume control. Its purpose is to allow the DAC stage to operate at a high output level, while the volume is managed by analog control placed after the vacuum tube amplifier stage. This solution can reduce noise level along with volume reduction, helping to improve the signal-to-noise ratio in real-world use.

From an audiophile perspective, hardware volume control is important because it provides finer and more natural level handling than solutions based solely on digital attenuation. This allows the Nunchaku to offer high output power while remaining precisely adjustable even with more sensitive earphones.

The Nunchaku’s operation is built around a 0.96-inch OLED display and a multifunction encoder. The display provides direct feedback on operation, while the control knob gives simple access to the device’s functions. This is especially useful in such a sophisticated dongle DAC, where precise control of output mode, gain and other settings defines the user experience.

The device can also be used with an Android app that offers additional adjustment options. Physical controls and software control together provide flexible operation, while the Nunchaku remains a compact, portable USB-C DAC/AMP.

The Nunchaku’s vacuum tubes are mounted using a suspended structure made with PORON material. Its purpose is to damp mechanical vibrations, which is especially important due to the sensitive structure of the JAN6418 tubes. The suspended installation reduces the microphonic effect and provides more stable operation during portable use.

Because vacuum tubes can vary individually, each tube pair requires careful matching. In the Nunchaku, JAN6418 tube pairs undergo SINAD-based pairing using an APX555 measurement system, so the operation of the two channels can remain as close as possible. This process preserves the vacuum tube character while offering more accurate stereo imaging and a more balanced sound.

The Nunchaku measures just 65 x 34.6 x 15 mm and weighs 50 g, making it easy to integrate into a smartphone, tablet or laptop-based listening system. Despite its compact housing, the device contains two DAC chips, vacuum tube and Class AB amplification modes, a balanced output, an OLED display and hardware control.

Power consumption is also a key consideration for a mobile USB DAC. In TUBE mode, the Nunchaku consumes 600 mW, while in Class AB mode it is slightly lower at half a watt. This efficiency allows the device to deliver serious amplifier performance while remaining easy to use with portable source devices.

Alongside the device itself, the Nunchaku package includes a case, USB-C to USB-C and USB-C to Lightning cables, plus a USB-C to USB-A adapter. The included accessories provide wider device compatibility, allowing the Nunchaku to be used with a range of digital sources.

Connection is USB-based, and the device converts the digital signal into a headphone-optimized analog output through its own DAC and amplifier circuits. With its 3.5 mm and 4.4 mm outputs, the Nunchaku remains both versatile and audiophile-focused, combining the character of vacuum tube sound with modern high-resolution processing.