iBasso Nunchaku Review – Vacuum Tube Portable DAC and Amp
The iBasso Nunchaku is a premium portable DAC and amplifier that combines cutting-edge technology with the charm of analog sound. Powered by two Raytheon JAN6418 directly heated vacuum tubes, it delivers a rich, warm, and engaging “tube flavor” in TUBE mode, while Class AB mode provides a clean, distortion-free experience. A dedicated 22.5V anode power supply ensures superior headroom and peak performance, enhancing audio fidelity.
At its core, the Nunchaku features a high-performance Cirrus Logic CS43198 DAC chip, a benchmark in conversion, and is renowned for its exceptional resolution, accurate sound reproduction, wide dynamic range, and exceptionally low noise floor. To minimize microphonic effects, the tubes are suspended using PORON material, reducing vibrations for pristine audio quality. Each unit undergoes APX555 testing to ensure meticulously matched tube pairs, with only 50 pairs completed daily, guaranteeing consistent, exceptional performance.
The Nunchaku features x2 Raytheon JAN6418 directly heated vacuum tubes, valued for their compact size, low power use, and reliability. Unlike typical portable devices with 5V or 12V power supplies, it uses a 22.5V anode power supply, ensuring superior headroom and optimal tube performance.
These tubes deliver a warm, smooth “tube sound” for an authentic analog listening experience. To reduce microphonic effects, iBasso suspends the tubes with PORON material, effectively minimizing vibrations and ensuring pristine audio quality.
For consistent sound, iBasso carefully matches the tubes using advanced APX555 testing, a meticulous process limited to 50 pairs daily, guaranteeing outstanding performance in every Nunchaku.
TUBE Mode: The Nunchaku’s sensitive tube design can produce a slight microphonic effect. If you tap the device’s chassis while music is paused, you may hear a ringing sound—this is normal. Additionally, there may occasionally be interference from nearby phones. However, when music is playing, these sounds are typically masked and do not impact the listening experience.
Class AB Mode: In Class AB mode, there is no microphonic effect, interference, background noise, or similar issues. Departing from the typical all-in-one chip approach found in most dongles, the Nunchaku adopts a sophisticated OPAMP+BUF634 flagship architecture. This design integrates x2 Raytheon vacuum tubes, x4 TI high-performance dual operational amplifiers (OPAMPs), and x4 BUF634A buffers into a compact footprint.
Nunchaku delivers up to 525mW+525mW@320Ω in TUBE mode, effortlessly powering flagship IEMs and most headphones. Despite its power, the Nunchaku remains energy-efficient, consuming just 120mA/5V in TUBE mode and under 100mA/5V in Class AB mode.
In TUBE mode, the Nunchaku incorporates a precise JRC hardware volume control. This innovative approach ensures the DAC operates at its MAX output level, followed by a tube amp stage and then volume control. This unique architecture effectively reduces noise as the volume is lowered, significantly enhancing the SNR and delivering a more refined listening experience.
Unboxing
Specifications
- DAC: Dual Cirrus Logic CS43198
- PCM: Up to 32bit/768kHz
- DSD: Native DSD 512x
- Weight: 1.7 oz
- Dimensions: 2.6″ x 1.4″ x 0.6″
4.4mm BAL Output (AB Mode)
- THD+N: -119dB (0.00011%) @1kHz 200kΩ
- Output Voltage
- 2.8Vrms (Low Gain)
- 4.1Vrms (High Gain)
- Output Power: 450mW@32Ω
- S/N: 130dB
- Dynamic Range: 130dB
- Crosstalk: 145dB
- Frequency Response: 15Hz-40kHz ±0.5dB
4.4mm BAL Output (TUBE Mode)
- Output Voltage
- 2.3Vrms (Low Gain)
- 4.5Vrms (High Gain)
- Output Power: 525mW@32Ω
- S/N: 107dB
- Dynamic Range: 110dB
- Crosstalk: 82dB
- Frequency Response: 15Hz-40kHz ±1dB
3.5mm SE Output (AB Mode)
- THD+N: -115dB (0.00017%) @1kHz 600kΩ
- Output Voltage
- 1.4Vrms (Low Gain)
- 2Vrms (High Gain)
- Output Power: 125mW@32Ω
- S/N: 125dB
- Dynamic Range: 125dB
- Crosstalk: 116dB
- Frequency Response: 15Hz-40kHz ±0.5dB
3.5mm SE Output (TUBE Mode)
- Output Voltage
- 1.15Vrms (Low Gain)
- 2.25Vrms (High Gain)
- Output Power: 150mW@32Ω
- S/N: 112dB
- Dynamic Range: 112dB
- Crosstalk: 82dB
- Frequency Response: 15Hz-40kHz ±1dB
Sound
The iBasso Nunchaku offers two distinct amplification modes, Vacuum Tube Mode and Class AB Mode. These modes provide slightly different sound signatures that can be instantaneously switched.
Let’s start with the Class AB Mode. In this mode, the iBasso Nunchaku sounds fairly balanced with dynamic and impactful bass, a fairly linear midrange, and a treble that is not sharp or as expansive as some of the dongles. The iBasso Nunchaku’s lower treble seems like it was tuned in a way that is inoffensive yet carries an adequate amount of detail. Its top-end extension is slightly rolled off, too, but it’s not by too much to hinder the detail retrieval.
Here’s a brief entry into the details of the VT (Vacuum Tube) Mode. In this case, the iBasso Nunchaku activates dual Raytheon JAN6418 tubes. The first difference that my ears picked up compared to the TM mode is the midrange. The mids feel more natural, with more instrument bodies and a better sense of soundstage depth. The bass response is smoothened with a slight decrease in depth and a slight increase in mass. The texture was smoother and felt similar, like going from snappy BA bass to big DD bass. The midrange feels much more natural. The lower treble is smoothened further in this mode compared to the Class AB Mode.
For most of the natural instruments, this is not an issue but a preference. Your matching IEM will matter here; I am writing these words whilst listening to it via MOONDROP Kadenz. I have also tested with the iBasso 3T-154, and that match was a bit better due to the iBasso 3T-154’s sharper pinna gain region and spicier treble compared to MOONDROP Kadenz. This dual-mode functionality provides flexibility that few other portable DAC/AMPs offer, making the iBasso Nunchaku a versatile unit that can be matched with a wide range of IEMs.
The standout for me is the VT mode, as it brings a noticeable richness to the mids, adding a natural, analog-like texture to vocals and instruments.
The treble, on the other hand, is smoothed out, which is nice. It avoids any harshness or sibilance while still retaining sufficient detail. Overall, this tuning gives you a musical, romantic signature that does not feel like it’s lacking any detail. The treble response in Class AB mode is slightly more pronounced than in VT Mode, delivering a tad bit more sparkle.
The soundstage, while not as spacious/holographic as in tube mode, maintains good width and height, depending on your pairing. I can’t say one is better than the other, as it depends on your personal preferences.
Sum-Up
The iBasso Nunchaku is an innovative product with excellent build quality and functionality. The Nunchaku features a unique blend of dual amplification modes, allowing users to switch between the richer tone of JAN6418 vacuum tubes and the more linear output of solid-state transistors (Cirrus Logic CS43198 DACs).
It’s super cool to have a portable DAC/Amp with both vacuum tubes whether I’m on the go, sitting around the house, or enjoying music in a coffee shop. The audio quality is outstanding. Given its high quality and reasonable price, I think this product is a worthy candidate for our collection.