If Building a 1920s Tube Amp Isn't Challenging Enough, How About Building the Vacuum Tubes Too?

Pseudonymous maker and vintage technology enthusiast "jdflyback" has built a retro tube amplifier — a project made even more impressive by the fact that the vacuum tubes it uses were built by hand alongside the amplifier.

Vacuum tube technology dates back to the early 1900s and John Ambrose Fleming's invention of a tube diode in 1904. For decades, the glowing glass tubes drove a range of electronic devices from radio and television sets to telephone networks and early room-filling computers. The invention of solid-state semiconductors, though, saw their popularity nosedive by offering a more reliable device in a smaller package at a lower cost operating at considerably improved efficiency.

Today, vacuum tubes — also known as valves — are primarily seen only in audio amplifiers, where their fans proclaim a "warmer" and more pleasant tone to modern solid-state electronics. It's for this reason jdflyback built a tube amplifier — but the project goes considerably further than most by constructing the tubes by hand too.

"This was a really fun project," the YouTuber claims in an hour-long overview of the work which goes into building vintage electronic components from scratch in your garage. The process might be fun, but it isn't easy: The tubes require spot-welding copper leads to nickel, creating a hermetic seal from tungsten wire, blowing glass into a flared tube, inserting the wires and heating the tungsten to create an oxide coating for the required seal.

Then the components need to be tailored to their application — a tight grid for the tube acting as a voltage amplifier to increase gain at the cost of supporting a lower current draw, and a looser grid for the tube that acts as a power amplifier so it won't burn out in the face of high current draw. A filament needs to be inserted and kept under tension using a spring, then everything is heated to push out the gas and create the vacuum required for the tube to operate without burning out.

In short, it's a project and a half — and that's before the rest of the amplifier is put together. Despite a failure of one tube which necessitated its replacement — "the tube that was going to be in this position got a pretty hard whack and ended up breaking its filament," jdflyback explains — the resulting amplifier is entirely functional with surprisingly acceptable sound quality despite the use of low-quality doorbell power transformers, and includes the reassuring glow of working vacuum tubes.

The full project video is available on jdflyback's YouTube channel.