【Feature 1】Techniques for Improving Listening Room Acoustics
Even the finest audio equipment cannot perform at its best in a room with poor acoustics. A purpose-built listening room is ideal, but in practice, we enjoy music in many different environments—from Japanese-style tatami rooms to Western-style interiors, in both timber and concrete buildings. This feature covers the fundamentals of acoustic treatment, listening evaluations of seven room acoustics accessories, and examples of structural improvements.
● The Fundamentals of Effective Acoustic Treatment — Yutaka Masaki
● Listening Evaluations of Seven Room Acoustics Accessories — Takashi Iwai and Koichi Hanzawa
・ACOUSTIC REVIVE RHR-21
・Takt Dice Cube J and Cubit J
・KRIPTON AP-R100
・ESCART DAP 120
・NiCSo Twofold SP
・Waecho acoustics CORNER
● Improving Room Acoustics, Part 2: Practical Improvements and Measurement Results — Kohei Suzuki
【Feature 2】Breakthroughs in Power Devices and Circuit Technology: Infineon GaN Class-D Amplifiers
600W × 2 into 4Ω from just four power semiconductor devices measuring 3 × 5mm each—with no heatsinks! We explore the ultra-efficient switching amplifier featured on this issue’s cover, alongside three amplifier builds using its evaluation boards and custom-built linear power supplies, complete with listening impressions.
● The Latest Developments in Infineon GaN Class-D Amplifiers — Isao Shibazaki
● Building Three Custom Power Amplifiers Using Infineon GaN Amplifier Evaluation Boards — Listening evaluations by Ikuo Tsunoda
・1200W board with an R-core power transformer and multiple smoothing capacitors — Built by Tokyo Electron Device
・750W board with a toroidal power transformer and high-capacitance smoothing capacitors — Built by Shinichi Katsuragawa
・750W board with a high-capacity power supply and an output low-pass filter using FINEMET cores and high-quality capacitors — Built by Kenji Tezuka
【Building Original Audio Systems】
Detailed design and construction guides for five tube power amplifiers using the E406N, EL34, SV83, 25E5, and 300B, ranging from beginner-friendly circuit-board builds to advanced designs. Also featured are a 5687 balanced line preamplifier and a desktop loudspeaker project that can be built for less than ¥10,000.
● E406N Single-Ended Power Amplifier with Cathode-Choke Drive
Bringing out the appeal of classic European tubes with cathode-choke drive and no negative feedback. — Masashi Yanagisawa
● EL34 Ultralinear Single-Ended Hybrid Power Amplifier
A simple configuration using an op-amp with a high output-voltage swing, with no capacitors in the signal path. — Yasuo Iwamura
● SV83 Push-Pull Power Amplifier
An experiment exploring the control capabilities of the suppressor grid in an output pentode. — Masaru Nagashima
● 25E5 Direct-Coupled Push-Pull Power Amplifier
Exploring a two-power-supply arrangement in a push-pull design using television tubes. — Susumu Soya
● 5687 Balanced Line Amplifier
A single-stage differential design using line transformers to eliminate output capacitors. — Hiroshi Ueno
● 300B SEPP DC Power Amplifier
A DC amplifier with a matching transformer, delivering a maximum output of 36W into 8Ω. — Akihiko Kaneta
● Computer-Assisted Audio Amplifier Design and Construction, Part 66
Configuring a miniDSP for a multi-amplifier system. — Heisuke Ikeda
● Designing and Building Compact Loudspeakers: A Desktop System for Less Than ¥10,000
Aiming for high efficiency and high sound quality. — Takahisa Ozawa
【Audio Technology】
● New York–Tokyo Audio Correspondence, No. 6: The Ever-Turning Wheel of Time
Can artificial intelligence move beyond conventional audio equipment design? — Devon Turnbull
● Circuit Design and Construction of the Luxman B-100 CENTENNIAL 125W/8Ω Monoblock Power Amplifier — Isao Shibazaki
● Measuring Tube Characteristic Curves, Part 7: Understanding Actual Performance Through Measured Data
Surprising similarities between the 2T12P and 801A. — Masaki Kubo
● Audio Equipment Repair Diary, Part 29: From Scrap to Working Equipment
Repairing the Sony TC-K71 three-head cassette deck. — Hideyuki Sakai
And much more!
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MJ Wireless and Experiment October 2026 Autumn Issue | Seibundo Shinkosha Publishing Co., Ltd. (seibundo-shinkosha.net)