iBasso AMP19

Nutube + Super Class A AMP Card for the DX340

• Plug-in Headphone Amplifier Card for the iBasso DX340
• Nutube 6P1 vacuum tube for a warm, analog tube character
• Two switchable output modes: Tube Mode and Super Class A Mode
• Up to 2150 mW + 2150 mW at 32 Ω with the 12V DC power supply
• JRC hardware volume control with 100 fine steps
• Every unit measured and matched using the Audio Precision APx555
• PORON suspension mount to reduce microphonic noise

Nutube 6P1 Vacuum Electron Tube

The AMP19 uses the sixth generation Nutube 6P1 triode vacuum tube, developed jointly by Korg and Noritake. It brings the well known sonic character of traditional tubes to a portable player, with a warm, natural sound and emotionally engaging vocals. Compared with traditional tubes, Nutube keeps the tube charm while being far better suited to long term, stable use in a portable device. Its lifespan exceeds 30,000 hours, it uses only about 2 percent of the power of a traditional tube, and it takes up only about 30 percent of the space.

Tube and Super Class A, Two Output Modes

The AMP19 offers two different output modes in a compact design. Whether you prefer the character of a tube or the high density sound of Super Class A, the AMP19 lets you switch easily between two distinct sound styles.

In Tube Mode, the Nutube 6P1 works as the preamp tube, adding harmonic richness to the sound. The tone is warmer, more relaxed and natural, vocals and instruments have a softer texture, and the overall presentation has an analog feel with a subtle glow.

In Super Class A Mode, 20 dual transistors form a discrete amplifier stage capable of delivering up to 2 A of current. This generous current reserve provides strong energy and dynamics, a fast transient response, a fuller sound, and excellent density and texture in vocals.

12V DC External Power Supply

The AMP19 uses a 12V DC-IN external power design that has been granted a national invention patent, patent number ZL 2025 1 0707956.3. With an external DC power source connected, the headphone amplifier supply rises from plus or minus 6.5 V to plus or minus 12 V, reaching 2150 mW plus 2150 mW at 32 Ω, enough to drive any flagship headphone with ease. The AMP19 is portable in form, yet it offers driving power comparable to a desktop unit, which is one of its key strengths.

JRC Hardware Volume Control, 100 Fine Steps

In Tube Mode, the AMP19 uses JRC hardware volume control, adjusting the output level by analog means so the DAC signal stays fully intact and digital volume attenuation is avoided, preserving audio fidelity. It clearly reduces output noise at low volumes, keeping the sound detailed and the music layered even at quiet listening levels. The volume control offers 100 fine steps for precise adjustment with highly sensitive in-ear monitors or high impedance headphones.

APx555 Precision Testing

The Audio Precision APx555 is a high performance audio analyzer known for highly accurate, low distortion measurements. Every AMP19 is tested with the APx555 before shipment, then calibrated and matched by hand using four hardware implemented multi-turn potentiometers, ensuring consistent operation of the Nutube 6P1. This preserves the natural, delicate, layered sound of the tube while delivering genuine analog character.

Note: using the AMP19 requires updating the DX340 firmware to version 1.08 or later.

PORON Suspension

After extensive experimentation, we adopted a suspended mounting method using PORON material to hang the tubes within the chassis. This approach absorbs shock effectively while significantly reducing microphonic effects.

Technical Specifications

Super Class A Mode

4.4 mm Balanced Output

Output Level: 8.3 Vrms (Super Gain), 5.8 Vrms (High Gain), 3.8 Vrms (Mid Gain), 1.8 Vrms (Low Gain)

Output Power: 2150 mW + 2150 mW @ 32 Ω (12V DC-IN), 1000 mW + 1000 mW @ 32 Ω (Battery)

THD+N: -109 dB (A-weighted, 300 Ω load)

Signal to Noise Ratio: 121 dB

Dynamic Range: 121 dB

Crosstalk: -114 dB

Frequency Response: 10 Hz to 40 kHz ±1 dB

Output Impedance: 1.4 Ω

3.5 mm Single-Ended Output

Output Level: 4.15 Vrms (Super Gain), 2.92 Vrms (High Gain), 1.89 Vrms (Mid Gain), 0.89 Vrms (Low Gain)

Output Power: 500 mW + 500 mW @ 32 Ω (12V DC-IN), 260 mW + 260 mW @ 32 Ω (Battery)

THD+N: -105 dB (A-weighted, 300 Ω load)

Signal to Noise Ratio: 110 dB

Dynamic Range: 110 dB

Crosstalk: -114 dB

Frequency Response: 10 Hz to 40 kHz ±1 dB

Output Impedance: 0.7 Ω

Tube Mode

4.4 mm Balanced Output

Output Level: 7.7 Vrms (Super Gain), 4.53 Vrms (High Gain), 2.92 Vrms (Mid Gain), 1.55 Vrms (Low Gain)

Output Power: 1850 mW + 1850 mW @ 32 Ω (12V DC-IN), 590 mW + 590 mW @ 32 Ω (Battery)

Frequency Response: 10 Hz to 40 kHz ±1 dB

Output Impedance: 1.4 Ω

3.5 mm Single-Ended Output

Output Level: 3.7 Vrms (Super Gain), 2.3 Vrms (High Gain), 1.49 Vrms (Mid Gain), 0.79 Vrms (Low Gain)

Output Power: 428 mW + 428 mW @ 32 Ω (12V DC-IN), 165 mW + 165 mW @ 32 Ω (Battery)

Frequency Response: 10 Hz to 40 kHz ±1 dB

Output Impedance: 0.7 Ω