There are certain components in vintage audio that stop being merely components. The Hitachi 2SK134 and 2SJ49 are among them. I encountered this complementary pair in a Japanese-market Luxman L-58A, and they are a large part of what makes that amplifier such an interesting machine. The L-58A isn't simply an old Luxman with MOSFETs bolted onto the output stage. It comes from that fascinating period when Japanese manufacturers were actively exploring what power MOSFETs could do differently—and...

In late 2022, I was contacted about a restoration project unlike anything I had taken on before. The customer had grown up in a house equipped with a large, vacuum-tube intercom and radio system built directly into the wall. Years later, while visiting the vacant property with his children, he discovered that the old intercom was still there. Knowing the house would eventually be demolished, he removed the unit and saved it. It was no longer simply an obsolete piece of electronics. It was a...

Crowbar Protection in Vintage Hi-Fi Amplifiers Fast, Violent, and Speaker-Focused Beyond fuses and relay protection, some vintage and semi-vintage amplifiers used a more aggressive—and frankly dramatic—method of speaker protection known as crowbar protection . It’s less common in consumer hi-fi than relays, but when it appears, it tells you a lot about the designer’s priorities: stop DC to the speakers at all costs—even if something has to die in the process . What Is Crowbar Protection? A...