Brise Audio FUGAKU - Ultimate Portable Audio System

FUGAKU'S BIGGEST FEATURE

It is a  Three-type hybrid drivers and a fully analogue multi-amp system .

The left side of the figure below is a simple example of the conventional method, and the right is a simple example of FUGAKU's multi-amp method.

In the conventional method, the amplifier → the passive filter → the driver are in that order, while in the FUGAKU method, the active filter → the amplifier → the driver are in that order.

In the traditional method, there is a band-splitting circuit called a passive filter between the amplifier and the driver, and the amplifier cannot directly drive the driver, and the directness of the sound is affected.

In addition, passive filters need to be made smaller to fit into the headphone housing, resulting in a simplified design.
As a result, it becomes difficult to achieve the ideal frequency response for the designer.

Since an amplifier drives multiple drivers, the more drivers you have, the lower the impedance, and the higher the load on the amplifier, the more distorted it is, and there are several negative elements in terms of sound quality in exchange for versatility.

To overcome these problems, FUGAKU introduced a multi-amp system.
This is a method that has been around for a long time in the world of speakers.

This is the world's first multi-amplifier configuration of hybrid driver earphones and is fully analogue, where each driver is driven by an amplifier prepared for each band.

It is no longer necessary to install the filter in the headphone housing and it is possible to use an advanced active filter consisting of OPAMP.

This makes it possible to compose a high-order steep filter, and it is possible to freely design the frequency response that most affects the sound quality. In addition, since a large amount of high-quality large-volume parts such as film capacitors can be used, it is possible to improve the quality of each component.

In addition, the driving force is high, and the sound can be realized with an unprecedented direct feeling because the amplifier and driver are directly connected. 

As the number of drivers increases, the number of amplifiers also increases, so the load per amplifier is low and distortion is less likely.

The expected disadvantages of this method are the flip side of the advantages of the conventional method.

Because it requires a dedicated amplifier and multi-pin cable, versatility is reduced and costs increase, but we chose this method because we felt the benefits in terms of sound quality far outweighed them.

In the multi-amplifier speaker system, it is necessary to prepare a preamplifier, an active filter and multiple power amplifiers separately, but by using these in a single cabinet, FUGAKU provides the ultimate sound with a sense of scale equivalent to the combination of conventional player + portable amplifier.

Product concept

The "ultimate earphones" that only Bliss Audio can produce were the beginning of FUGAKU.

And the concept is that when we do it, we want to achieve the quality that we want most, and we want to create a composition that is not bound by any existing framework, with sound quality being the top priority.

When it comes to a unique configuration with an advantage in sound quality, the idea of ​​bi-amplified driving with a dedicated portable amplifier first came to my mind.

However, if we were able to develop everything in-house, we could do something better by incorporating band splitting into a portable amplifier, so we thought the FUGAKU multi-amp system was born.

FUGAKU classifies "quality" into three categories: "sound quality", "design" and "comfort", and to achieve all of this at a high level, we have developed various ways of using headphones, special portable amplifiers and dedicated cables.

As for the sound quality we strive for, "expressing all the information of the source" is consistent with FUGAKU.

The excellent physical properties of the optimal structural design through the reasonable use of multiple driver types and the sound quality directly driven by a high-performance band divider circuit and multiple high-performance amplifiers turned our common sense upside down and left a strong impression that we had never experienced before.

These earphones are a high-level fusion of conventional drivers such as  the dynamic headphone type and the balanced armature type and a new driver called MEMS speaker.

Because the active crossover is built into the dedicated portable amplifier, there is no crossover in the headphone body, and each driver and amplifier are directly connected.

The 3D sound pipe, titanium shaft and gold-plated OFC ring integrated into the 3D printed driver unit holder provide excellent physical properties as well as the optimal parameter setting of the active crossover, resulting in an acoustic performance that blends smoothly across the entire band.

Based on years of experience in designing, developing and manufacturing custom and universal IEMs, we have created a housing shape that is comfortable to wear and soundproof.

By using the cable with the bottom and ear hook type, the deviation of the rotation direction is suppressed and extremely high wearing stability is achieved even though it is a universal earphone.

A specially designed 7-pin cable is used to connect the cable. Although it is small and has few multi-contacts, it has a design that harmonizes with the headphone body and gives a sense of unity.

Dedicated portable amplifier

This is a portable amplifier for FUGAKU that balances compactness and durability while giving top priority to sound quality.

Based on TSURANAGI's feedback, the differential line receiver and electronic volume were rewired, the power amplifier was refreshed, and a new circuit was introduced.

In order not to compromise comfort, the interior is designed three-dimensionally to achieve the same size as TSURANAGI. 

The main board is a two-story structure with two parts, and the first floor is a four-layer board mainly for power supply circuits and control circuits, and the second floor is an eight-layer board with only analog circuit amplifiers.

From the main board to the input/output ports, it is wired with pure silver wire made of the same wire material as the dedicated cable.

A total of 10,000 μF or more capacitance capacitors are effectively placed in the power supply circuit, contributing to the sound quality with a low center of gravity. In addition, in order to thoroughly avoid interference between circuits, up to 14 ultra-high-performance linear power supply circuits are implemented.

To receive the signal of  dedicated cable amplifier To transmit the signal to each driver without loss, it is a 16-core cable with pure silver conductors that was developed exclusively for this system.

By using a newly developed high-purity pure silver rolled wire, it achieves a high level of flexibility and user-friendliness as well as excellent sound quality despite its multi-core.

Based on the pure silver wire tuning method developed by SHIROGANE, we have applied dedicated Ultimate-quality high-quality sound processing.

Beautiful appearance and high wearing stability

Based on the experience of developers who have been engaged in the production of custom IEMs and earphones for many years, the headphone part of FUGAKU has created a housing design that combines wearing comfort and aesthetics with industrial designers.

The case material is pure titanium, which features high strength and moderate resonance with few metal-specific peculiarities, and a black PVD coating is applied to the surface to improve durability.

The three slots, which represent the three pillars of the cable, the amplifier and the earphones, reveal a gold-plated OFC ring that houses the dynamic driver and expresses the combination of black and gold, the company's corporate colors.

One of the main features of this earbud is that it has an ear hook type, but if you use a so-called secure hanging cable above your ear, the earbud may shift in rotation direction during use due to the weight of the cable etc. or the cable may bite into the ear base and become painful. To solve this problem, we chose an ear hook type.

The cable is extended downward and the downward force is supported by the TPE ear hanger to improve mounting stability.

The earrings have built-in memory wires that can also be adjusted for bending.

In addition, since it is a multi-amplifier system, it is necessary to connect each amplifier output and each driver independently, but since there was no connector that could harmonize with the design of the headphone case due to the large number of pins and the small size of 7 contacts, we developed an original connector.

The cable attachment and detachment structure is designed to be replaceable in the event of disconnection, and in principle the customer is not expected to replace it himself.

The included earbud is made of AZLA XELASTECII, which has an excellent fit and seal.

All 6 sizes come with 1 pair each. To experience the excellent low frequency expression of FUGAKU, it is very important that the left and right sides are tightly sealed, so please find a suitable size.

Bandwidth allocation and selection of the right  Driver for the right task

Based on our experience in manufacturing and developing custom IEMs and universal IEMs, we have found that the best way to divide the band, ieLowrange, mid-low range, mid-high, high range, high range and ultra-high frequency, is optimal for the best band distribution in terms of mounting scale and easy generation of good characteristics.

For the lower range, it is equipped with a Φ8mm dynamic driver that uses a liquid crystal polymer diaphragm.

The two dynamic drivers are attached to each other in an OFC ring.

By using an opposite arrangement, it is possible to suppress unnecessary vibrations associated with the operation of the diaphragm, and by distributing the load with two drivers connected in series, low distortion, good response and a profound low frequency range are realized.

The OFC ring is also gold plated to protect the surface and keep it smooth.

It is equipped with a total of 3 types of 5BA drivers: a single BA from Sonion in the mid and low range, a dual BA from Knowles in the mid range and one in the high range.

For ultra-high frequencies, we used xMEMS side-port MEMS speakers.

The high responsiveness of the piezoelectric process and the broadband reproduction characteristics improve the atmosphere, delicacy and realism of the sound.

It uses the reverse piezoelectric effect which deforms the piezoelectric film when voltage is applied, and since the piezoelectric film itself is made of silicon wafers and vibrates and produces sound, it is smaller and more responsive than DD and BA which drive the diaphragm by electromagnetic induction of the coil, and there is very little variation as there are no mechanical parts to assemble.

Layout that achieves the ideal frequency response

Each driver is attached to the bracket of the screwdriver unit of a 3D printer (purple part) with integrated sound channel and integrated into the housing.

The sound emitted by the device holder is synthesized on the shaft of the titanium case to form the final sound.

The design of the mount and stem aligns the phase of each driver and resonates the sound to position the peak dip, creating a sound that is the base tone for creating a sound with an active crossover.

It is one of the key components in achieving the three-dimensional sound of FUGAKU, and there has been a lot of trial and error.

Because MEMS speakers are small and thin, it is easy to secure space for sound lines in other bands even when placed close to the outlet, allowing for optimal routing.

The OFC rings that secure the two dynamic drivers are also connected to the sound tube of the tubular low-pass filter structure of the device holder.

In addition, the sound-absorbing material is placed on the back of each dynamic screwdriver and on the inside of the arm-shaped protruding part to which the earring hangers are attached.

By absorbing and dampening the sound emitted from the rear port of the dynamic driver and the rear vent of some BA drivers and reverberating inside the cabinet, the sound re-enters and affects the operation of the diaphragm, improving the clarity of the low frequencies.

FEATURES DEDICATED PORTABLE AMPLIFIER

Based on  TSURANAGI  This amplifier has been greatly improved by adding a crossover and reviewing the circuitry.

The first improvement is that we introduced a low-pass filter in the first stage.

In TSURANAGI, the power amplifier in the last stage also served as a low-pass filter, but by bringing it to the first stage, the overall noise was reduced.

Since there is no bandwidth limiter in the power amplifier, this also contributes to improved responsiveness when driving headphones.

The capacitor used in this low pass filter is a special type called an X2Y capacitor, a well-matched capacitor specialized for processing balanced signals.

There is an IC that switches between unbalanced and balanced inputs before the low-pass filter, and all inputs to the low-pass filter are balanced signals.

This structure is the same as that of TSURANAGI, but by using a semiconductor switch with very low resistance and low distortion instead of a toggle switch, we have added a function for automatically selecting input terminals along with a function for inserting and removing terminals.

The differential line receiver is also a new circuit different from TSURANAGI, and the performance has been improved by dividing the single IC into two ICs.
As a result, the residual noise here is less than 1/5.

The electronic volume is also evolving and we have updated it to a new Japanese wireless MUSES72323.
This improves the feeling of air and freshness required for high-end devices.

In addition, the volume has been halved from 0.5 dB steps to 0.25 dB steps, allowing for finer volume adjustment.

The buffer amplifier is an OPAMP with FET inputs, and the electronic volume minimizes the current output and minimizes distortion, and the crossover has a large capacity capacitor, so it plays a role in fixed driving.

Power amplifiers are configured differently than dynamic drivers or otherwise.
In addition, a DC bias circuit is added to the power amplifier that drives the MEMS driver.

First of all, the power amplifier that drives the dynamic driver is a circuit that combines and drives a pure differential amplifier and a current feedback amplifier in the same configuration as TSURANAGI while converting it into a balanced signal.

The plus α is that the components used have been redesigned to achieve lower output impedance and improved drive performance.

In the power amplifiers other than the dynamic driver, a voltage feedback amplifier is used in a completely new circuit.
This is also intended to drive headphones and has excessively high power for headphones.

Although not shown in the figure, a DC servo amplifier is also integrated into a power amplifier other than MEMS to eliminate AC coupling capacitors in FUGAKU.

The component limits of the DC servo amplifier were reviewed and the feedback method to the power amplifier was further simplified and the number of components was reduced to low noise.

As shown in the power supply circuit block diagram above, we designed an original low noise circuit based on a linear regulator for the DC bias circuit for MEMS.