Overview

The Yamaha B-1 is a vintage stereo power amplifier manufactured from 1975–1978, representing Yamaha’s flagship V-FET design alongside the NS-1000M speakers. Utilizing first-generation V-FET devices, it is specified at 150 watts per channel (20Hz–20kHz, both channels driven) and 160 watts per channel at 1kHz [1][2]. Total harmonic distortion (8Ω): 0.02% at 1kHz and 0.06% at 20kHz at 100W output; 0.02% at 1kHz and 0.03% at 20kHz at 1W output [2]. The amplifier weighs approximately 83 pounds (37kg) and has a rated power consumption of 440W [2].

Scientific Validity

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Based on manufacturer specifications, the B-1 achieves THD of 0.02% at 1kHz and 0.06% at 20kHz (8Ω, 100W), with 150W/ch (20Hz–20kHz) and 160W/ch (1kHz) output ratings [2]. These values exceed the transparent threshold of 0.01% THD at full power. No credible modern third-party measurements (e.g., complete AP/SINAD sweeps) are available, so absolute performance versus contemporary state-of-the-art remains unverified. Modern amplifiers routinely achieve SINAD >100dB and THD+N <0.005%. Given the lack of comprehensive modern measurements, this evaluation follows the 0.5 baseline with consideration of known limitations.

Technology Level

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The B-1 represented advanced engineering in 1975–1978 with its V-FET output devices and period topology. However, the first-generation V-FET implementation lacks the sophistication of modern designs. Contemporary amplifiers using latest semiconductor technology, advanced feedback systems, and optimized power supply designs achieve vastly superior measured performance. The complex pre-driver circuitry required for non-complementary V-FET pairs indicates design constraints of the era rather than advancement.

Cost-Performance

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Current market price ranges from 995–3,000 USD for working units depending on condition. Taking 2,000 USD as a representative market price, equivalent-or-better performance is available from a Fosi Audio V3 Mono pair. Per unit price: 109.99 USD; required power supplies: 48V/5A each at 59.99 USD [3][4]. Total for a working stereo pair: (2 × 109.99 USD) + (2 × 59.99 USD) = 339.96 USD, delivering 240W into 4Ω (per channel) with THD+N <0.006% and SINAD up to 101dB (XLR) [3]. Cost-performance ratio: 339.96 USD ÷ 2,000 USD = 0.170, rounded to 0.2.

Reliability & Support

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As a ~50-year-old vintage amplifier, the B-1 lacks official manufacturer support and replacement parts availability. The V-FET devices are obsolete and difficult to source. High idle power and heat generation potentially reduce component lifespan. No warranty coverage exists for vintage units, and specialized repair expertise is increasingly rare. Long-term reliability is questionable due to aging electrolytic capacitors and thermal stress on components.

Rationality of Design Philosophy

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Substantial idle power and heat (rated power consumption 440W) provide no scientifically demonstrable advantages over modern efficient designs. When transparent performance is achievable via modern Class‑AB or Class‑D implementations at a fraction of the power and cost, the associated heat and energy use are difficult to justify. The V‑FET pursuit does not deliver measurably superior results compared to contemporary designs achieving transparent levels of distortion and noise. The design philosophy prioritizes historical significance over practical audio performance.

Advice

The Yamaha B-1 appeals primarily to vintage audio collectors rather than those seeking optimal sound quality. Modern alternatives like the Fosi Audio V3 Mono deliver equivalent power with vastly superior measured performance at approximately 17% of the cost. The B-1’s historical significance as Yamaha’s V-FET flagship cannot justify its current market pricing for practical audio reproduction purposes. Consider modern alternatives for transparent audio performance without the operational costs and reliability concerns of vintage equipment.

References

[1] Yamaha B-1, HiFi Engine Manual Library: https://www.hifiengine.com/manual_library/yamaha/b-1.shtml (accessed Aug 2025) [2] YAMAHA B-1 仕様（オーディオの足跡）: https://audio-heritage.jp/YAMAHA/amp/b-1.html (accessed Aug 2025) [3] Fosi Audio V3 Mono product page: https://fosiaudio.com/products/fosi-audio-v3-mono-power-amplifier (accessed Aug 2025) [4] Fosi Audio 48V 5A & 10A Power Supply Unit: https://fosiaudio.com/products/power-supply-adapter-48v-5a-10a (accessed Aug 2025)

(2025.8.10)