iBasso Nunchaku Portable DAC and Tube Amplifier

The iBasso Nunchaku is a portable USB DAC and headphone amplifier with two real vacuum tubes inside, and a choice of sounds. Tube mode uses two Raytheon JAN6418 tubes for a warm, sweet, analogue sound; Class AB mode gives higher resolution and abundant dynamics. Two Cirrus Logic CS43198 DACs and iBasso’s FPGA handle PCM up to 768kHz/32-bit and native DSD512, and a flagship-style op-amp and buffer stage delivers up to 525mW per channel into 32Ω.

Dual Raytheon JAN6418 tubes with a 22.5V anode supply

The JAN6418 is a directly heated tube known for its compact size, low power consumption and stability. Where most portable tube products use 9V or 12V, the Nunchaku has a dedicated 22.5V anode supply for more headroom, so the tubes work at their full potential and give a distinctly analogue sound: warm, laid-back and smooth.

Tube or Class AB

Switch between the two output modes to suit your music: tube mode is sweet and warm, with rich, even harmonics; Class AB mode uses high-precision op-amps with BUF634A buffers for higher resolution and dynamics, with no microphonics or tube background noise.

Flagship-style amplification

Instead of the all-in-one amplifier chip most dongles use, the Nunchaku has the op-amp and buffer structure of flagship players: four Texas Instruments high-performance dual op-amps and four BUF634A buffers alongside the tubes. Tube mode gives up to 525mW + 525mW into 32Ω, enough for any flagship IEM and most headphones, yet power use is low: about 120mA at 5V in tube mode and under 100mA in Class AB mode.

Dual CS43198, FPGA and femtosecond clock

Two of Cirrus Logic’s flagship CS43198 DACs work in a balanced layout, with iBasso’s in-house FPGA and a KDS femtosecond oscillator for precise timing.

JRC hardware volume control

In tube mode the DACs run at full output so the tubes amplify the strongest possible signal, and a JRC hardware volume control then lowers the level, taking the noise down with it for a much better signal-to-noise ratio.

PORON suspension and hand-matched tubes

After many attempts, iBasso suspends the tubes on PORON material, absorbing shocks and reducing microphonics on the move. Because tube production varies slightly, iBasso pairs every set of JAN6418 tubes by SINAD on an Audio Precision APx555 before it goes into a Nunchaku, a process so thorough that it is limited to 50 pairs a day.

Simple controls

A 0.96-inch OLED screen and a multi-function knob control everything on the device, and an Android app adds further settings. There are 4.4mm balanced and 3.5mm single-ended outputs, and the 3.5mm socket can also act as a coaxial digital output.

Good to know

• As iBasso explains, the tube filaments can be slightly microphonic: tapping the case while music is paused may cause a faint ring, a phone close by may cause minor interference, and tubes have some background noise. These are usually masked by music; Class AB mode has none of them.
• In the box: Nunchaku, protective case, USB-C to USB-C and USB-C to Lightning cables, and USB-C to USB-A adapter. Red or grey.