Audio DesignLine Blog
Audio amp design: Do you tube?
Rich Pell
8/6/2007 9:58 PM EDT
Probably like most people who learned engineering after the 1970s I was never formally taught anything about vacuum tubes. They'd long since been relegated to the electronics history books.
But I had been studying, designing and building all manner of do-it-yourself (DIY) audio projects long before I ever set foot in an engineering class. So although I hadn't actually built anything with tubes at that point, I'd seen my share of schematics sporting those recognizable but still mysterious - and intriguing - symbols.
And it had been one of the projects I had built - a DIY electrostatic loudspeaker (ESL) published in Audio Amateur - that had led to my first piece of tube audio equipment. It was a home-built hybrid solid-state/tube direct-drive electrostatic loudspeaker amplifier with an 8068 beam pentode output stage, and I obtained it from the author of the ESL article himself, who had since switched to using a conventional solid-state audio amplifier with step-up transformers to drive his ESLs.
It was huge, weighed over 50 lbs, and was an excellent apartment heater. Nonetheless, it and the ESLs it drove produced some great (although highly directional) sound, with an equally great soundstage. Symphonic music and Pink Floyd's The Wall never sounded so good!
Still, while I enjoyed the amp's sound and the glow of its tubes in the dark, I'm sure I would have enjoyed it just as much had it been all solid state. After all, the use of tubes in that ESL amplifier was mostly a matter of necessity based on its direct-drive design requirements - not a conscious decision on the part of the designer to choose a valve design over a readily available solid-state solution.
In fact I might easily have managed to avoid the lure of further tube audio projects altogether, except for the fact that my interest in sound and music reproduction extended to the niche market of high-end audio. And like any good card-carrying audiophile, I knew that those glowing electron-emitting relics of the past were (and still are) hot commodities in that rarified realm.
Part 2 of this post (to be posted shortly) concludes with a few more of my tube adventures, including a DIY tube DAC, and some tube audio resources.
Comments, questions or suggestions? Email me at rich.pell@verizon.net.
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