The TSURANAGI portable amplifier

TSURANAGI-V2 is a Version 2 model improved based on feedback obtained from TSURANAGI. Noise level has been halved and improved to play more subtle sounds. The three main changes are “6dB reduction in gain,” “volume curve change,” and “change to laser engraving.

The TSURANAGI portable amplifier was developed as an evaluation unit for the development of Brise Audio’s high-end earphone cables and high-end portable line cables (mini-mini cables) in order to create an ideal portable audio environment. Brise Audio cables are used for internal wiring, and the electromagnetic wave absorbing shielding material and CNT (carbon nanotube) used in our high-end cables MURAKUMO and YATONO are installed on the board to further improve the sound quality.

A composite amplifier handles both conversion and current amplification

The TSURANAGI-V2 is a portable amplifier designed for the growing use of balanced LINE OUT and balanced headphone drive. It supports both balanced (4.4mm/2.5mm) and unbalanced (3.5mm) inputs, converting unbalanced signals to precise balanced output. Featuring low distortion, low noise circuits, and a high input impedance of 1MΩ, it ensures clean playback even in noisy environments. A composite amplifier handles both conversion and current amplification, while current feedback and ultra-low-noise regulators further reduce distortion. Built on a 6-layer board, it delivers wide bandwidth, high output, and a very low noise floor—serving as Brise Audio’s reference amplifier for cable development without compromising sound quality.

Amplifier Configuration

Other innovations regarding the amplifier were to set the amplifier bandwidth from 2 Hz to 200 kHz to ensure flat reproduction in the audible bandwidth of 20 Hz to 20 kHz.

The amplifier’s 2 Hz–200 kHz bandwidth ensures flat audio reproduction. A differential DC servo amplifier suppresses DC offset to ±50µV, eliminating input coupling capacitors and preserving sound quality. Ultra-low-noise OPAMPs and a microcontroller-based DC protection system safeguard earphones. High-grade film and polymer aluminum capacitors are used for power decoupling, with all components carefully selected for maximum sound quality, regardless of cost.

Independent power supplies

The TSURANAGI-V2 uses independent power supplies for left and right channels to ensure channel separation and sufficient current delivery. Dual power rails are generated from the battery with a 2 MHz switching regulator and large capacitors for low-noise operation, followed by ultra-high-performance linear regulators that remove residual switching noise. Operating at ±9.3V balances high performance with battery life, while a 6-layer PCB design with separated power, ground, and signal layers minimizes interference. Grounding is carefully managed to eliminate loops and external electromagnetic noise, ensuring clean, low-distortion output.

These linear regulators are capable of rejecting noise down to the high-frequency bandwidth, so even 2 MHz switching noise is reliably removed.
Two of the six layers are used for power supply, and the layers are separated by positive and negative, with a GND layer in between to prevent interference.
As with the power supply, GND wiring is also routed on a plane to reduce impedance, while signal GND and power GND are separated not only between channels but also within a channel to the point where they intersect at a single point to ensure thorough separation.
It is grounded to the aluminum chassis at a single point to eliminate GND loops while suppressing external electromagnetic interference.

The figure shows the case where TSURANAGI had an all-stage balanced configuration and the configuration of a product that performs unbalanced conversion.