Overview

Lo-D (Lord) was a high-end audio brand developed by Hitachi from the 1970s to 1980s. It is known for the HMA-9500 stereo power amplifier (released in 1977), which was the world’s first to use power MOSFETs, representing revolutionary technology for its time. The brand offered a wide range of products including amplifiers, speakers, phono cartridges, and turntables, with custom speakers like the HS-1500/5000/10000 ultra-high-end models. However, production has ceased and products are only available on the used market.

Scientific Validity

\[\Large \text{0.3}\]

The HMA-9500’s nominal specifications (100W+100W/8Ω, frequency response 5Hz-100kHz) were excellent for 1977 standards but problematic compared to modern measurement standards. Being analog circuitry, it cannot remotely achieve the transparent levels that modern digital amplifiers realize: THD below 0.01%, SNR above 105dB, and crosstalk below -70dB. The MT series phono cartridges (such as MT-24) with frequency response 10Hz-25kHz and 3mV output remain at 1970s standards, causing audible degradation compared to modern high-precision digital measurement equipment.

Technology Level

\[\Large \text{0.3}\]

The technology was advanced for the 1970s, featuring the world’s first power MOSFET adoption (HMA-9500), proprietary Unitorque motor technology (turntables), and jewel bearing systems (cartridges). The three-stage differential amplifier design, independent left/right power supplies, and capacitor elimination in NFB loops were rational approaches for the era’s technical standards. However, from modern technical standards, it significantly lags behind digital control, high-precision clocks, 32-bit DACs, and Class D amplifier technology, making it obsolete technology.

Cost-Performance

\[\Large \text{0.1}\]

While used HMA-9500 units trade in the 25,309-160,000 yen range, the Fosi Audio BT20A Pro (11,000 yen) achieves vastly superior measurement performance with equivalent 100W output: frequency response 20Hz-20kHz ±1dB, THD ≤0.005%, SNR ≥108dB. The cost-performance calculation shows that the Fosi Audio costs approximately 1/7th the price while delivering superior specifications, resulting in an extremely poor cost-performance rating for Lo-D products. MT series cartridges at approximately 10,000 yen used versus Audio-Technica VM95E (11,000 yen) offering equivalent or superior performance. Vintage value is irrelevant to measurement performance, so pure sound quality performance-to-price ratio is significantly inferior to modern products.

Reliability & Support

\[\Large \text{0.2}\]

With over 40 years since production ended, there is no manufacturer support whatsoever. Parts procurement is difficult, and repairs require specialized technicians when failures occur. Being analog circuitry, aging degradation is unavoidable, with continuous maintenance costs such as electrolytic capacitor replacement. While built robustly for products of that era, it significantly lags behind the long-term warranties, firmware updates, and parts supply systems that modern products provide.

Rationality of Design Philosophy

\[\Large \text{0.3}\]

While the design was rational within the limitations of 1970s analog technology, numerous irrational elements exist from a modern perspective. Analog circuit-inherent distortion, noise, and crosstalk are fundamentally unavoidable, and in an era where complete transparency through digital processing is achievable, there is no scientific basis for deliberately choosing analog equipment. Like vacuum tubes and analog records, it represents an irrational choice accepting measurable sound quality degradation. Smartphone + external DAC combinations can achieve equivalent or superior functionality with vastly superior measurement performance.

Advice

Purchasing Lo-D products cannot be recommended for sound quality improvement purposes. A modern 11,000 yen Class D amplifier completely surpasses an 80,000 yen vintage Lo-D amplifier in measurement performance. It only becomes a consideration for those who find value in vintage equipment collection or historical significance, but this is subjective value unrelated to sound quality. For practical purposes, choosing modern products with the same budget will yield vastly superior measurement performance and reliability. Beginners especially are strongly advised to prioritize objective sound quality improvement based on measurement data and not be misled by brand or history.

(2025.7.21)