If you happen to’ve ever puzzled what goes into making a vacuum-tube audio amplifier, maker Mike Freda has the reply — obtained by actually constructing one from scratch.
“I scratch [built] an built-in stereo tube amplifier utilizing PSVane 12AU7-AT and 6L6WGC-AT tubes,” Freda explains of his newest challenge. “For this amplifier design I [did] one thing a little bit bit out of the field. I have never actually seen something like this carried out earlier than. This amplifier [is] designed as an built-in amplifier. I do not plan to make use of a pre-amp with it, for the reason that 12AU7s haven’t got plenty of amplification issue. I will be utilizing each triodes to get sufficient voltage swing to moderately drive the 6L6.”
Vacuum tubes have been as soon as the inspiration expertise for all the pieces from radios and amplifiers to early computer systems, however their excessive energy draw and unreliability meant that the invention of the solid-state transistor consigned them to the historical past pile — for all, that’s, besides audiophiles, who consider them to supply a richer, hotter sound than you may obtain with fashionable parts. Some select to seek out new-old inventory; others, like Freda, decide up new tubes from the few producers nonetheless remaining.
Freda’s construct utilizing the 2 aforementioned tube sorts, plus a meaty transformer able to delivering the 700V required to make them sing. The rest of the parts, together with capacitors, resistors, and the mechanical connections for audio system and an audio supply, are all housed in a custom-designed casing. “I ended up making a separate plate that may mount on the within,” Freda explains of the structure, “and can home all of the terminal strips and tube sockets, and this shall be recessed down so once you put the tube sockets in it can type of recess into the chassis a bit and provides it extra of a 3D look.”
There’s surprisingly little contained in the case, with the vacuum tubes protruding for aesthetic attraction. (📷: Mike Freda)
“Upon some longer listening periods,” Freda concludes of the construct, “I discover that this amp has a deep bass, impartial mid-range with a pronounced top-end sound attribute. This may occasionally change because the parts burn in, keep tuned!”
The challenge is documented within the video embedded above and on Freda’s YouTube channel; a invoice of supplies and schematic can be found on Google Drive; “please be at liberty to repeat, regulate, modify to your coronary heart’s content material,” Freda says of the license underneath which they’re made accessible, “that’s what is finished right here.”