Fancy a Brand New Tube Amp? Follow Mike Freda's Scratch-Build Project, and Make One Yourself

A quartet of brand new vacuum tubes drives this custom stereo amplifier with "deep bass, neutral mid-range, and pronounced top-end."

Gareth Halfacree
3 months agoMusic / Retro Tech

If you've ever wondered what goes into making a vacuum-tube audio amplifier, maker Mike Freda has the answer — obtained by literally building one from scratch.

"I scratch [built] an integrated stereo tube amplifier using PSVane 12AU7-AT and 6L6WGC-AT tubes," Freda explains of his latest project. "For this amplifier design I [did] something a little bit out of the box. I haven't really seen anything like this done before. This amplifier [is] designed as an integrated amplifier. I don't plan to use a pre-amp with it, since the 12AU7s don't have a lot of amplification factor. I'm going to be using both triodes to get enough voltage swing to reasonably drive the 6L6."

While transistors have ruled the roost for decades, there's still a market for new vacuum tubes — as Mike Freda's amp build proves. (📹: Mike Freda)

Vacuum tubes were once the foundation technology for everything from radios and amplifiers to early computers, but their high power draw and unreliability meant that the invention of the solid-state transistor consigned them to the history pile — for all, that is, except audiophiles, who believe them to offer a richer, warmer sound than you can achieve with modern components. Some choose to find new-old stock; others, like Freda, pick up new tubes from the few manufacturers still remaining.

Freda's build using the two aforementioned tube types, plus a meaty transformer capable of delivering the 700V required to make them sing. The remainder of the components, including capacitors, resistors, and the mechanical connections for speakers and an audio source, are all housed in a custom-designed casing. "I ended up creating a separate plate that will mount on the inside," Freda explains of the layout, "and will house all the terminal strips and tube sockets, and this will be recessed down so when you put the tube sockets in it will kind of recess into the chassis a bit and give it more of a 3D look."

"Upon some longer listening sessions," Freda concludes of the build, "I find that this amp has a deep bass, neutral mid-range with a pronounced top-end sound characteristic. This may change as the components burn in, stay tuned!"

The project is documented in the video embedded above and on Freda's YouTube channel; a bill of materials and schematic are available on Google Drive; "please feel free to copy, adjust, modify to your heart's content," Freda says of the license under which they're made available, "that is what is done here."

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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