table jockey - I surmise, from your comment concerning vacuum tubes, that you’re a relatively young man, at least young enough that you did not have to suffer through those terrible times when vacuum tubes were the sole means of building anything electronic. I’m now 86, and not nearly so fortunate. My interest in “hi fi”, as we then referred to this hobby, first sparked in 1949, right at the beginning of the LP record era. My life, in the course of the next 5 years, left no opportunity to pursue hi fi, but that changed in early ’54, when I got back to NY from the Korean War. And from that time forward, I became quite active in my pursuit of high quality audio. Of course, this meant embracing vacuum tubes. Transistors (germanium alloy) were then in their infancy, and unsuitable for serious use, so tubes were the sole option. And I soon learned that tubes were imperfect—they had high failure rates, and the heat from their filaments cooked the other components—and that this problem could work well for me if I learned radio/TV repair. So I built a (kit) tube tester and oscilloscope, and an oscillator, and bought a multimeter, and I began a 32 year career in electronics.
I soon learned that, although some circuits were better than others, the basic variability of tubes made for lots of design compromise. Tubes are simply not high precision devices. Tube parameters are initially expressed, by their makers, as typical characteristics, not as absolute limits. And their variable performance is inconsistent. Tubes forever change as they age. Filament temperatures vary, cathodes continuously disintegrate, grid spacing shifts—and tubes constantly degrade, from the moment that they’re first turned on until the day that they fail. Tubes are simply not dependable.
All of those tube shortcomings were tolerable to me when they were inside somebody else’s radio or TV set, but I hated to see ’em in my own audio gear. I once purchased a costly hi-end Fisher FM-200B tuner, one of the very best available, but its RF and IF stages kept drifting due to tube aging. I had to perform complete RF realignments every 6 months. And my Marantz 8B stereo power amplifier needed constant rebiasing of the output tubes to keep the IM distortion to within 0.5%, and I’d install four new EL34s every 20 months or so. Indeed, I got so anxious to dump vacuum tubes that I finally built my own solid state power amplifiers (dual mono units) back in the mid ’70s, just as soon as PNP silicon power transistors became commercially available. So I happily left vacuum tubes behind forever, in the past, where they belong!
The state of vacuum tube technology has severely regressed in the 40+ years since I kissed tubes goodbye. All of the former domestic, British, Dutch, and German makers of tubes are now either defunct (like Tung-Sol Electric, my employer from March of ’57 to March of ’60), or they ceased production long ago. The remaining world market for vacuum tubes is now limited exclusively to (young) audiophiles, and it’s served only by a few recent Russian and Chinese suppliers who had no prior production credentials. (I believe that there might also be a supplier in Ireland.) The general quality and consistency of product coming from these unregulated foreign sources is dubious, and they’ll exist only for the duration that audiophile demand will support.
The future for vacuum tubes looks dicey—especially since all measurable means of evaluating quality supports the superiority of solid state design. It’s only a select subset of you young audiophiles—guys who feel that their ears are more accurate than any instrumentation—that makes selling tubes viable. Like I said, it’s dicey.
