In the long history of digital audio development, the evolution of DAC chip technology has always been an important force driving the industry forward. We have witnessed the transition from single-bit to multi-bit, from discrete architectures to highly integrated single-chip solutions, with each technological breakthrough redefining the limits of sound reproduction. In recent years, the most notable DACs in the market have been ESS Technology’s SABRE series and AKM (Asahi Kasei Microdevices)’s VERITA series chips. ESS’s flagship DAC, the ES9039PRO, boasts the highest dynamic range in its class, reaching 140dB (A-weighted), with THD+N at -125dB, and supports DSD1024, PCM1536kHz, and MQA hardware decoding. Meanwhile, AKM’s AK4499EX requires pairing with the AK4191 to form a separated DAC processing solution, known for its “warm” tonal quality and analog flavor.

Of course, while the ESS flagship DAC chip has extremely high performance specifications, devices equipped with it are often described by audiophiles as “scientific machines,” with a cold and hard “digital flavor” sound evaluation accompanying many devices using this chip. However, this does not reflect the true capabilities of this DAC chip. In a range of flagship HiFi devices, through better matching of front and rear digital processing circuits, high-quality power systems, and well-tuned analog amplification components, this flagship ESS DAC chip can achieve a perfect blend of specifications and sound quality, delivering an impressive audio performance.

On the other hand, the AKM AK4499EX is renowned for its unique tonal charm, but in many models, we often see a “sacrifice of full-frequency balance to achieve a prominent density and thickness, leading to a lack of overall coherence; when the vocal density is sufficient, the instrument’s texture becomes dull, and when the instrument’s texture is pronounced, the vocals may sound thin or lacking in depth.”

The significant differences in actual performance stem from the design of the DAC itself. While ESS’s “Quad-DAC” architecture is high-performance, it still requires manufacturers to implement I/V, LPF, and gain stages themselves. This design offers greater tuning freedom but undoubtedly tests the digital and analog circuit design skills of the manufacturer’s engineers. In contrast, AKM’s approach is more straightforward, providing only fixed filters, which limits tuning flexibility. This explains why devices using ESS chips exhibit a wide variety of sound performances, while those using AKM chips tend to have a more uniform sound style, albeit sometimes appearing somewhat rigid when the design is not sufficiently thorough.

Now, let’s return to the main character of this article: Cirrus Logic. Cirrus Logic was founded in 1981 by Dr. Suhas Patil in Salt Lake City as Patil Systems Inc., and was renamed Cirrus Logic after moving to Silicon Valley in 1984. In 1991, Cirrus Logic acquired Crystal Semiconductor (a supplier of AD/DA ICs), bringing classic audio codecs like the CS4231 and CS4614 from the PC sound card era into its fold, laying the first cornerstone for “Hi-Fi on computers,” which also marked the beginning of the “CS” series DACs. It is important to note that unlike traditional DAC chip manufacturers like TI/Burr-Brown or Motorola, Cirrus Logic has a more sophisticated and cutting-edge approach to mixed-signal processing technology, with a series of innovative designs that also give Cirrus Logic’s CS series chips a significant advantage in power consumption control, enabling their widespread application in portable audio.

If you are a seasoned HiFi enthusiast, the Cirrus Logic CS series DAC chips will surely be familiar to you, as they are unavoidable for most users. As early as the 1990s, chips like the CS4328 were already used in many well-known CD players and digital audio devices. These chips, with their warm and delicate tonal characteristics and excellent linear performance, have won the favor of many audio engineers and audiophiles. The emergence of the CS4398 in the early 2000s marked Cirrus Logic’s technological maturity in the high-end audio DAC field. This chip, with its exquisite multi-bit architecture and extremely low distortion characteristics, became a common choice for professional audio equipment and high-quality CD player/DAC decoders at the time. With the evolution of digital audio technology, Cirrus Logic launched new generation products like the CS4399 and CS43198 in the 2010s, which significantly improved performance while maintaining the brand’s signature tonal style, adapting to the demands of the high-resolution audio era.

The Launch of the New Flagship DAC and Its First Application

In 2024, Cirrus Logic launched the all-new CS4308P chip, the company’s latest flagship DAC chip in response to competitive pressures from ESS and AKM. It features a 32-bit resolution, 8-channel digital-to-analog converter, supports sampling rates up to 768kHz, with a dynamic range of 123dB and THD+N below -114dB. Nine segments have carefully studied its technical architecture, and the CS4308P adopts Cirrus Logic’s unique analog finite impulse response (FIR) architecture, effectively reducing out-of-band noise while minimizing the need for external components. Notably, the CS4308P includes a manually programmable digital filter, allowing engineers to finely adjust frequency response characteristics, providing device manufacturers with greater tuning flexibility, which is the standout feature of the HiBy R6 Pro II 2025 that will be discussed later.

The application of a manually tunable digital filter allows HiBy’s designers to endow the HiBy R6 Pro II 2025 with mainstream flagship-level sound quality while maintaining sufficient family sound understanding and tonal performance compared to similar products at the same price point or even higher. In the past, achieving similar performance, whether using ESS chips or AKM products, required more coordination of front and rear digital and analog circuits, which undoubtedly led to significant increases in size and cost. This is why we see similar performing models, such as the HiBy R8II and AK SP3000, mostly appearing in flagship products priced over ten thousand yuan and positioned at a higher tier.

Additionally, compared to other flagship DAC chips on the market, the CS4308P’s energy efficiency and integration maintain the family’s consistent advantages and also have considerable latecomer advantages. Its proprietary current steering architecture ensures it has the lowest power consumption performance among currently available flagship DAC chips under full performance operation, clearly distinguishing it from the ES9039Pro and AK4499EX (it should be noted that due to that fire, the 4499 still requires pairing with the 4191 to complete all functions). At the same time, the current steering architecture also offers significant advantages in portable audio devices, allowing for richer design possibilities in the backend analog amplification circuit. HiBy engineers have also successfully applied this feature, fully integrating the high-performance analog amplification circuit with switchable Class A/AB operation mode used in the flagship R8 series into the new HiBy R6 Pro II 2025. The excellent high current output capability allows this new player to easily deliver 632mW (32Ω) of power through the 4.4mm balanced output, a significant increase from the previous model’s 383mW, and more importantly, achieving high standards comparable to the R8 series in terms of distortion, background noise, signal-to-noise ratio, and dynamic range.

Sound Performance: The Art of Stability and Power

After discussing the technical specifications, let’s talk about the sound performance of the HiBy R6 Pro II 2025, the industry’s first music player equipped with the CS4308P DAC, allowing everyone to intuitively feel the impact of DAC chip technology advancements on our actual music appreciation experience. Firstly, the new HiBy R6 Pro II 2025 maintains a 5000mAh battery, but the standby time has increased from 600 hours to 750 hours, undoubtedly benefiting from the new DAC’s extremely low power consumption performance. At the same time, the new device is equipped with a Qualcomm Snapdragon 665 processor and the latest version of the HibyOS music system based on Android 12, featuring four output interfaces: 3.5mm/4.4mm independent PO/LO, and supports coaxial output, bidirectional Bluetooth, USB DAC, and other functions. It can be seen that, whether in configuration or functionality, although still called “R6 Pro,” it has fully approached the ten-thousand-yuan “R8” series.

After long listening sessions, I found that the sound characteristics of the HiBy R6 Pro II 2025 can be summarized in two keywords: “stability” and “power.” The so-called “stability” is reflected in the fact that regardless of the headphone style paired, the initiative is always in the hands of the HiBy R6 Pro II 2025, demonstrating strong control. If the headphones have bright and stimulating highs, with sharpness and intensity, the HiBy R6 Pro II 2025 will moderately suppress the originally aggressive and overly vibrant feel, keeping it within a comfortable listening range for the human ear, expressing the necessary brightness and extension while avoiding most dissonant factors. This sense of stability is also well displayed in the mid-frequency vocal section; I even believe that the vocal tuning of this machine leans towards reference level, as it does not deliberately bring the distance closer or overly thin and cold, but rather focuses on polishing sibilance and imaging positioning. With a thick and cohesive style and distinct layering, a relaxed feeling naturally arises, allowing for a real reproduction of vocals that combines warmth and charm.

The “power” can be clearly experienced when the new machine is first turned on. At first listen, you may sense the high quality of this machine but find it difficult to pinpoint its standout features. However, as you listen more closely, you will gradually discover that this player follows a “ready to unleash” approach in terms of power reserves, capable of releasing an exceptionally strong sense of energy when needed. Thanks to the increased driving power, although it is only a mid-range product, it rarely encounters insufficient driving capabilities with earplugs and portable headphones, especially in the low-frequency performance, which far exceeds all other music players in its class. As long as the headphones are not severely impaired in terms of volume, they are likely to receive a powerful and majestic feedback, and the low-frequency rebound speed of this machine is exceptionally clean and crisp.

Practical Compatibility Experience: Surprising Versatility

In practical use, I tried using the HiBy R6 Pro II 2025 to drive various types of headphones, from easy-to-drive in-ear headphones to portable over-ear headphones that require more power. The results were surprising—632mW of balanced output power indeed played a significant role. When paired with HiBy’s own tenth-anniversary commemorative earphones, The Golden 10th, the lively and enthusiastic style of these earphones was fully showcased, with outstanding vocal expressiveness and impressive low-frequency ambiance. The soundstage was wide, with accurate positioning of different sound elements and clear sense of distance, highlighting high-density quality features.

Even more surprisingly, the R6 Pro II 2025 can even drive some portable large headphones, such as the HIFIMAN GL1000P, which has a strong sound enveloping quality, with energy concentrated in the mid-high range. Under the drive of the R6 Pro II 2025, it can perfectly present the headphone’s vibrant high frequencies while also excelling in the texture and elasticity of the low frequencies, allowing one to experience the solid performance of low-frequency energy, which is quite challenging for the GL1000P. At the same time, switching to the Beyerdynamic DT990Pro X, the R6 Pro II 2025 can endow it with a considerable density of full-frequency detail and a quick, tight mid-low frequency texture. Although this differs slightly from the DT990Pro X’s inherent style, it must be acknowledged that the changes imparted by HiBy’s engineers are both pleasant and enjoyable.

Final Thoughts: A New Benchmark in the Mid-High-End Market

The industry’s first application of the Cirrus Logic CS4308P not only makes the HiBy R6 Pro II 2025 a milestone product in the mid-range portable player market but also proves HiBy’s profound expertise in audio technology integration. This is not just a routine hardware upgrade but a concentrated reflection of Cirrus Logic’s decades of technological accumulation. The CS4308P, with its unique architectural design and excellent energy efficiency, provides HiBy engineers with ample room for creativity, allowing them to achieve a significant improvement in sound quality while maintaining the brand’s tonal heritage.

In terms of actual listening experience, the CS4308P exhibits not only parameter advantages but also a profound understanding of the essence of music. It retains Cirrus Logic’s consistently warm and delicate sound foundation while providing sufficient resolution and dynamic performance, a balance that is rare in the mid-range market. HiBy engineers have cleverly utilized the programmable digital filter of the CS4308P, integrating the brand’s understanding of sound into it, creating a sound performance that embodies both the brand’s own tonal understanding and rich musical expressiveness.

From a market positioning perspective, the emergence of the R6 Pro II 2025 redefines the standards for mid-range players. It not only aligns its performance with high-end products but, more importantly, offers a rare level of completeness and maturity among products in the same price range. For music enthusiasts, this product represents a rare choice: it does not require paying a premium for high-end products while still providing a near-flagship level music experience.

Finally, the HiBy R6 Pro II 2025 maintains the “slim waist” design of the R6 Pro series, but the new light blue color is quite understated and elegant, which Nine segments would call the “most beautiful HiBy” today.