IBASSO AMP13 Korg Nutube 6P1
Interchangeable amplifier module for iBasso DX300 and DX320 players
The iBasso AMP13 module is designed to provide an alternative amplification system for the iBasso DX320 and DX300 digital music players, allowing for a different sound to suit individual tastes. Here, the AMP13 uses a Korg Nutube 6P1 tube amplifier stage to provide a smooth and rounded sound, with the addition of a second amplifier stage to boost the module's performance.
6th generation Korg Nutube
The 6th generation Nutube from KORG and Noritake works exactly like a traditional triode tube and offers the same features, including rich harmonics. In addition, Nutube offers lower power consumption, significant miniaturization and quality improvements over standard tubes.
The iBasso AMP13 completes the voltage amplification through the Nutube, delivering a round and warm sound while maintaining excellent linearity.
Dual 3.5mm output
However, the voltage amplification capabilities of the Nutube 6P1 are limited. Two levels of gain are required to achieve comfortable performance. So, in order to take advantage of the tube's sound and good power handling, the AMP13 uses a dual 3.5mm jack output with a low-noise tube output, and a second jack output that offers higher power.
Low noise tube output:
AMP13 uses Nutube 6P1 voltage amplifier. This is followed by a digital volume control and current amplifier. This low-noise tube output comes immediately after the first stage of amplification. It allows you to further exploit the sound shapes offered by the tube amplification and has excellent noise control (2.5 Vrms).
Maximum performance:
This second output goes through the Nutube gain stage first, followed by a second gain stage. It allows the AMP13 to take advantage of higher voltage and current amplification, so it can be used with most headphones (4.1 Vrms).
Three amplifier channels
The single-ended output of conventional players usually has only two channels of amplification. Here, to enhance the performance of the Nutube 6P1, the AMP13 uses three-channel amplification. The OPA1622 PDO amplifies the output ground signal, allowing a significant reduction in background noise while improving the dynamics and capabilities of the tube amplification.
Dedicated battery and dual DC-DC power supply
The DX320/DX300 amplifier section has its own dedicated battery power supply, perfect for powering the AMP13 module. The AMP13 uses two of Linear Technology's high performance DC-DC chips for a total of four DC-DC power supplies. The first provides 1.8 V to the cathode via a low-noise LDO, the second provides 21 V to the Nutube anode, and the last two provide +8 V and -8 V, respectively, to form the 16 V voltage resonance that powers the AOP.
Optimised architecture
- Toshiba 2SK209 surround transistor for Nutube output buffer.
- To avoid noise from interference, separate the signal and shielding.
- Negative feedback to the amplifier circuit for effective distortion reduction and wider frequency response.
- The addition of dedicated JRC ultra-low noise control reduces background noise at low volumes and improves transparency.
Manually tested and adjusted
All AMP13 units are tested and optimised using an AP audio analyser. Three multi-turn potentiometers on the board are calibrated and matched by engineers for optimum performance. As a result, the AMP13 delivers clean high frequencies and an overall even, balanced sound.
