Ancient Web: Direct Heating Kept Susumu Sakuma's Vacuum-Tube Philosophy Online

Part of the Ancient Web Collection.

Some audiophiles argue about measurements. Susumu Sakuma built unusual vacuum-tube amplifiers, invited people to listen, and preferred the music to settle the argument.

Visit the Direct Heating archive.

The homepage calls Direct Heating a society for listeners who enjoy the Sakuma system, and its visitor counter starts on September 24, 1996. It is still updated, but its internal pages retain old image navigation, schematic diagrams and photographs of immense tube amplifiers. The site announces that Sakuma died in December 2018 and that his restaurant, Concord, is closed.

The biography places that restaurant in Tateyama, a train journey from Tokyo. Customers expecting dinner encountered handmade amplifiers instead. Sakuma, born in 1943 according to the page, treated reproduced music as something with an emotional force that could not be reduced to a circuit diagram.

The amplifier as an argument with a listening room

The amplifier explanation admits that many Japanese audio enthusiasts disagreed with Sakuma's design choices. He favored transformers and unorthodox circuits, departing from approaches recommended in many engineering references. The page describes his experiments with Lowther speakers and his increasingly personal approach to shaping their sound.

This should not be confused with proof that his preferred circuitry was technically superior. Its value is that the website lets him and his supporters explain their reasoning in their own terms.

An amplifier gallery pairs photographs with tiny downloadable circuit figures, including 801A/845 and VV300B designs. Other directories hold speaker experiments, concert photographs, phono equipment and a Japanese–English dictionary for amplifier builders last updated in November 1996.

The society's account says it was established in 1980 and that Sakuma's writing appeared in the magazine MJ Musen to Jikken. It also recalls concerts abroad in Milan and Paris. The attendance figures on the biography are the organization's own estimates, not independently audited totals.

Even the more recent homepage updates are archival: it notes the 2025 end of transformer production by Tamura and links to recordings of Sakuma's poetry uploaded by his daughter. The webpage survives as a meeting place for a community whose central craftsman is gone.

Browse the preserved amplifier photographs and circuits.

Part of the Ancient Web Collection.