Overview

The Fosi Audio V3 is a stereo power amplifier equipped with the Texas Instruments TPA3255 Class D amplifier chip. Its most notable feature, rare at this price point, is the implementation of PFFB (Post-Filter Feedback) technology, which resolves the frequency response variations caused by speaker impedance, a common issue in traditional Class D amplifiers. Claiming a maximum output of 300W×2ch (at 4Ω), it is designed for serious performance despite its compact form factor. Established in 2017, Fosi Audio is a rapidly growing Chinese audio manufacturer known for its high-value, cost-effective products.

Scientific Validity

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In detailed measurements by Audio Science Review (ASR), the V3 records an excellent SINAD (Signal-to-noise and distortion ratio) of 102dB into a 4Ω load. This figure significantly surpasses the problematic level and approaches the “transparent” threshold in our measurement criteria table (equivalent to THD+N well below 0.01% or -80dB). Thanks to the PFFB technology, the frequency response is almost perfectly flat from 20Hz to 20kHz, regardless of the connected speaker’s impedance. It also delivers ample power, measuring 158W into 4Ω and 88W into 8Ω (at 1% THD+N). While early production units had a polarity inversion issue, this has since been corrected. Overall, it demonstrates exceptionally high scientific validity for its price.

Technology Level

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While the core TPA3255 chip is an existing technology released in 2016, the application of PFFB to solve the load dependency issue is a commendable technical refinement. The internals feature high-quality components, including Japanese Nichicon/ELNA capacitors, German WIMA capacitors, and Japanese Sumida inductors, which enhance its fundamental performance. However, the basic circuit design is based on Texas Instruments’ recommended reference design, limiting its innovation in terms of proprietary circuit technology. It skillfully combines existing technologies to achieve high measured performance, but it does not represent top-tier proprietary engineering, placing its technology level as above average.

Cost-Performance

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The V3 (with a 48V power supply) sells for approximately 16,000 JPY on Amazon Japan. The crucial point for this product’s evaluation is that there are no cheaper products on the market that feature PFFB and achieve equivalent or superior measured performance (SINAD >100dB, flat frequency response). For instance, the popular Aiyima A07 (approx. 12,000 JPY), while using the same TPA3255 chip, lacks PFFB and is thus inferior in performance, as its high-frequency response can vary depending on the connected speaker. Therefore, the V3 is effectively the world’s lowest-priced amplifier in its performance class, earning a perfect cost-performance score of 1.0.

Reliability & Support

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As a relatively new company founded in 2017, Fosi Audio is still building its long-term reliability track record. It offers a warranty period of 18 months, which exceeds the industry standard and can be extended to 24 months with user registration on their official website. While this is commendable, details about local repair centers and prompt support systems in regions like Japan are unclear. On the product quality front, an output polarity inversion issue in early units suggested challenges in quality control, although the company responded swiftly once the problem was identified. The reliability and support are standard for an emerging brand, with expectations for future improvements.

Rationality of Design Philosophy

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The approach of pursuing high efficiency and compactness with Class D technology while overcoming its weakness of load dependency via PFFB is a highly rational design philosophy directly contributing to sound quality. The strategy of using the proven TPA3255 chip and high-quality off-the-shelf components to achieve high measured performance while keeping costs down is also logical. However, it lacks technological breakthroughs or unique innovations, remaining an excellent combination of existing technologies. Furthermore, with only RCA inputs and no balanced connection option, there is room for future evolution. It is a rational product for maximizing cost-performance, but its innovativeness is standard.

Advice

The Fosi Audio V3 is a choice that dominates others in the sub-20,000 JPY price range in terms of measured performance. The flat and stable frequency response, courtesy of PFFB, is a significant advantage when pairing it with various speakers. It is an ideal option for users looking to build a powerful yet compact desktop audio or stereo system. When purchasing, it is highly recommended to select the model with the 48V power supply to unlock its full performance potential. Although the input is limited to RCA unbalanced connections, this will not be an issue for most applications. This is an extremely high-value product that offers near-transparent fidelity at an unbeatable price.

(2025.7.23)