Aune Audio BX2 Magnum Portable Headphone Amplifier

The Aune BX2 Magnum is a portable headphone amplifier with two genuine Korg Nutube 6P1 vacuum tubes, a fully balanced four-channel Class A circuit, and up to 5 watts of output into 32 ohms, running entirely on its own seven-cell battery bank. Almost nothing else you can fit in a jacket pocket attempts this.

The BX2 Magnum is built for listeners who refuse to choose between a serious rig and a portable one. Feed it from a DAP, portable DAC, or desktop source through 3.5mm, 4.4mm balanced, or RCA inputs, and it drives IEMs and full-size headphones from 3.5mm and 4.4mm outputs with a choice of two completely different sonic characters.

Two Amplifiers in One Chassis

A physical switch selects between tube mode and transistor mode, and the two signal paths are fully independent, joined only by latching relays that switch without coloring the signal. Transistor mode is the precision path: linear, fast, and measurably clean at 0.0003% THD+N from the balanced output. Tube mode routes the signal through the Nutubes for the warmth, body, and harmonic richness tubes are loved for, with distortion up to 1% because that character is the entire point.

Two gain levels and two Class A current settings multiply those characters further. Between mode, gain, and bias, the BX2 Magnum offers eight distinct operating combinations to match headphones and mood.

Real Tubes, Properly Driven

The Korg Nutube 6P1 is a true dual-triode vacuum tube, and in the BX2 Magnum both tubes sit genuinely in the amplification stage rather than glowing decoratively behind a window. A dedicated 30V anode supply pushes them into their optimal linear range, the voltage headroom portable tube stages usually lack. Ahead of them, a twin JFET input stage adds its naturally smooth transfer characteristic, and the fully balanced four-channel layout keeps left and right isolated for precise imaging.

Seven Batteries, Each with a Job

Power is the reason the BX2 Magnum sounds like desktop gear. Its 14,000mAh battery bank uses seven independent 2000mAh cells: six form a true plus and minus 12V analog supply feeding the amplifier directly, while the seventh runs the digital control circuits in complete isolation, keeping control noise out of the music. Two four-segment indicators on the rear panel track both banks in real time.

A full charge over USB-C takes about five hours and delivers up to 13 hours in transistor mode or more than 8 hours in tube mode, enough for a work day on the solid-state path or a long evening on the tubes.

A Desk Mode, Thanks to the BP1

A five-pin external power input lets the BX2 Magnum bypass its battery entirely and run on plus and minus 15V from Aune's BP1 external power supply, sold separately and built in the same stackable chassis. On the desk it runs at higher rails than the battery provides while the cells sit idle; on the move the battery takes over again. One amplifier honestly covers both lives.

Measured Like a Desktop Amp

The numbers hold up against amplifiers that never leave a shelf: output noise of 3 microvolts or less, signal-to-noise ratio above 117dB, and a 31-step R2R digital volume control that keeps channels matched at low listening levels with no contact noise. High gain delivers 5,180mW balanced into 32 ohms and 644mW into 300 ohms, so hard planars and high-impedance dynamics both stay on the menu. Check your own pair against the table below with our headphone power calculator.

How the BX2 Magnum Compares

Its closest relative is Aune's desktop S17 Pro EVO, which shares the twin JFET input and Class A philosophy with more raw power and a wall socket. The BX2 Magnum is the version of that idea you can take with you, and it adds something the desktop amp does not have: real vacuum tubes and a second sonic personality. In the portable amplifier category, that combination has essentially no direct rival at $799.

Key Features

• Portable Class A headphone amplifier with tube and transistor modes
• Dual Korg Nutube 6P1 vacuum tubes, genuinely active in the signal path
• 30V anode supply runs the tubes in their optimal linear range
• Fully balanced four-channel discrete architecture with twin JFET input
• Physically independent signal paths with latching relay switching
• Up to 5W into 32 ohms; 5,180mW balanced at high gain
• Two gain levels and two Class A current settings
• 14,000mAh seven-cell battery: six cells for +/-12V analog, one for digital
• Up to 13 hours battery life in transistor mode, over 8 hours in tube mode
• External power input for the BP1 power supply (sold separately)
• 31-step R2R digital volume control with precise channel matching
• 3.5mm, 4.4mm balanced, and RCA inputs; 3.5mm and 4.4mm outputs
• Output noise 3uV or lower; SNR above 117dB
• All-aluminum CNC chassis in black and gold
• USB-C charging at 5V/2A
• Hi-Res Audio certification

Technical Specs

Headphone Output Power (High Gain)

What's in the Box

• Aune BX2 Magnum portable headphone amplifier
• 3.5mm to 3.5mm cable
• 4.4mm to 4.4mm cable
• USB-C to USB-C charging cable
• Velvet pouch
• 4 spare silicone feet
• Quick start guide and warning card