The AMP19 is a card designed specifically for the DX340, so you can replace the heart of the sound while keeping the player's form and handling. The module is compact, and the package includes a screwdriver and four screws for installing it.

Using the card requires updating the DX340 firmware to V1.08 or later. The module offers a 4.4 mm balanced and a 3.5 mm single-ended headphone output, and the external power connects to the 12 V DC-IN input.

The Nutube brings the renowned sonic qualities of traditional tubes to a portable player: a warm, natural sound with emotionally engaging vocals. It keeps the charm of classic tubes, but is far better suited to long-term stable use than a traditional tube.

The sixth-generation Nutube 6P1 triode tube, developed jointly by Korg and Noritake, has a lifespan of over 30,000 hours, consumes only 2% of the power of traditional tubes and is roughly 30% of their size. In Tube mode it acts as the preamp tube and adds harmonic richness to the sound.

In Tube mode the Nutube 6P1 acts as the preamp tube and adds harmonic richness to the sound: the tone is warmer, more relaxed and more natural, vocals and instruments have softer textures, and the overall picture is more analogue, with a charming glow. In Super Class A mode, an amplifier that emphasises the density and power of the sound takes over.

The Super Class A mode uses a discrete amplifier built from 20 dual transistors, capable of delivering up to 2 A of current. The abundant current reserve provides powerful energy and dynamics, quick transient response, a fuller sound, and excellent vocal density and texture.

The block diagram clearly shows that the AMP19 combines two complete signal paths: the output selector decides whether the sound reaches the headphone amplifier through the Nutube branch or the Super Class A transistor branch. The Nutube has separate anode and filament power supplies.

According to the diagram, the Nutube 6P1 receives separate 22.5 V DC anode and filament power supplies, the signal path includes the OPA, the JRC volume IC and a phase inverter, and the Super Class A branch is built from transistor pairs. Power comes from the battery, through a DC-DC converter, or via the 12 V DC-IN input, with ±6.5 V or ±12 V rail voltage.

In Tube mode the AMP19 uses JRC hardware volume control, which adjusts the volume in an analogue way, so the sound stays clean and detailed even at low volumes and the layers of the music are preserved. The 100 fine steps allow precise adjustment on high-sensitivity in-ear monitors and high-impedance headphones alike.

The analogue control leaves the DAC signal fully intact, avoids digital volume attenuation and thus preserves audio fidelity. It effectively reduces output noise at low volumes and plays a key role in taming tube noise.

The tubes are suspended inside the chassis with PORON material, so the module effectively damps vibrations. This protects the clarity of the tube sound and makes the module more robust.

After extensive experimentation, iBasso adopted the "hanging" installation method, which, in addition to shock absorption, significantly suppresses the microphonic effect, the noise generated by mechanical vibration of the tube.

Every AMP19 is tested before shipping and calibrated and matched by hand by engineers, so the sound is consistent from unit to unit. The natural, delicate, layered tube sound is preserved, and you get an authentic analogue flavour.

The Audio Precision APx555 is an audio analyser renowned for its high-precision, low-distortion measurements. The consistent operation of the Nutube 6P1 is set with four hardware multi-turn potentiometers.

The short video shows the AMP19 amplifier card, which gives the DX340 player a new sound world. The card's Nutube tube mode and Super Class A mode live together in a single module.

The AMP19 offers a 4.4 mm balanced and a 3.5 mm single-ended output, with a 10 Hz-40 kHz ±1 dB frequency response in both modes. The technical data is in the tables below.