On Vacuum Tubes—Then and Now...

By Bryan Geyer

I returned from Korea in early 1954, and soon became absorbed in the new “hi fi” craze. Of course, that meant embracing vacuum tubes. Transistors were very new—not ready for prime time—so tubes were the sole option. Tube failures were common, and their heat would often cook some of the adjacent components, but I reasoned that those faults could be my gain if I learned basic radio/TV repair, so I built (from kits) a tube tester, a signal oscillator, a simple oscilloscope, and I bought a new Simpson model 269 multimeter. That marked the start of my 32 year career in the electronics industry.

Do recognize that vacuum tubes are not high precision parts. Why not? Well, to start, all of the tube makers present their products only by listing generic “average” or “typical” performance data. They don’t provide (or control) any of the specific operating characteristics*, so vacuum tubes of a given type can vary widely. Further, all tubes exhibit a constant, gradual, and persistent life cycle drift; plate current fades, grid bias shifts. So a tube’s functional day-to-day performance is never precisely the same. This natural cyclic drift starts when the tube initially enters service, and ends when the tube dies from cathode depletion failure—barring all of the many other modes of premature demise that might intervene (e.g.: open filaments, vacuum leaks, gassing, microphonics, atypical distortion, excessive hum/noise, and damage from external mechanical shock). As a consequence, vacuum tube circuits are not the best means to assure stable circuit performance; there’s simply no optimally constant operating phase. Regardless, for some 70 years tubes were all that we had. Circuit design got stale toward the end of that era because the chassis space available for tube sockets limited potential complexity; also because tubes are so woefully inefficient. But creative innovation blossomed when PNP silicon power transistors finally debuted in the mid 1970s, thereby making complementary differential solid state symmetry a plausible alternative.

Personal angst: In 1963 I bought a Fisher FM200B tuner, one of the premier signal-seekers of the day, but its IF stages exhibited incessant drift due to tube aging. I had to perform tedious IF realignment annually. And my 1962 Marantz 8B stereo power amplifier needed semi-annual output stage bias adjustment to hold the measured IM distortion inside 0.5%, plus I had to install four new EL34 output tubes every 2 or 3 years; that’s costly! Indeed, I got so hot to dump vacuum tubes that I finally built my own solid state power amps in 1976, when PNP silicon power transistors finally became affordable. (Refer p.39 of https://www.americanradiohistory.com/Archive-Radio-Electronics/70s/1973/Radio-Electronics-1973-03.pdf.) Hey, I was free at last!

Vacuum tube commerce has collapsed in the ensuing 43 years. All of the domestic, British, Dutch, and German producers are now either defunct (like Tung-Sol, my employer from ’57-’60), or they ceased making tubes decades ago. The entire world market for audio-type tubes is now confined solely to the needs of select audiophiles and guitar buffs, and currently fulfilled only by obscure producers in China, Russia, and Slovakia. All are without previous market recognition. The quality, consistency, and reliability of product from those arcane foreign sources is speculative, and supply will persist only as long as there’s viable demand, so the outlook for affordable access to replacement stock looks dicey. Further, this status prevails at a time when all audio engineers concur that the load-invariant advantage assured by driving the loudspeaker from an ultra-low impedance source is dependent on solid-state design. (The Zout for a solid-state power amp runs < 1/10th of the Zout for a tube amp.) Today’s audio-type vacuum tubes represent the detritus of a dead technology; it’s time to move on.

*Refer any vacuum tube specification sheet. For example, here’s the published data for type 6550, a common power output tube: https://shop.ehx.com/catalog/addimages/6550-tung-sol.pdf. Note that there are no minimum or maximum limits given for any of the various operating characteristics. (This traditional practice is in direct contrast with the semiconductor industry, wherein complete min./max. acceptance criteria is provided for almost every critical parameter on every registered device.)

BG (May 2019)

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Meet the Staff

Meet the Staff
John J. Puccio, Editor, Publisher, Reviewer

Understand, I'm just an everyday guy reacting to something I love. And I've been doing it for a very long time, my appreciation for classical music starting with the musical excerpts on The Big John and Sparkie radio show in the early Fifties and the purchase of my first recording, The 101 Strings Play the Classics, around 1956. In the late Sixties I began teaching high school English and Film Studies as well as becoming interested in hi-fi, my audio ambitions graduating me from a pair of AR-3 speakers to the Fulton J's recommended by The Stereophile's J. Gordon Holt. In the early Seventies, I began writing for a number of audio magazines, including Audio Excellence, Audio Forum, The Boston Audio Society Speaker, The American Record Guide, and from 1976 until 2008, The $ensible Sound, for which I served as Classical Music Editor.

Today, I'm retired from teaching and use a pair of bi-amped VMPS RM40s loudspeakers for my listening. In addition to writing the Classical Candor blog, I served as the Movie Review Editor for the Web site Movie Metropolis (formerly DVDTown) from 1997-2013. Music and movies. Life couldn't be better.
Karl W. Nehring, Contributing Reviewer

For more than 20 years I was the editor ofThe $ensible Soundmagazine and a regular contributor to its classical review pages. I would not presume to present myself as some sort of expert on music, but I have a deep love for and appreciation of many types of music, "classical" especially, and have listened to thousands of recordings over the years, many of which still line the walls of my listening room (and occasionally spill onto the furniture and floor, much to the chagrin of my long-suffering wife). I have always taken the approach as a reviewer that what I am trying to do is simply to point out to readers that I have come across a recording that I have found of interest, a recording that I think they might appreciate my having pointed out to them. I suppose that sounds a bit simple-minded, but I know I appreciate reading reviews by others that do the same for me -- point out recordings that I think I might enjoy.

For readers who might be wondering about what kind of system I am using to do my listening, I should probably point out that I do a LOT of music listening and employ a variety of means to do so in a variety of environments, as I would imagine many music lovers also do. Starting at the more grandiose end of the scale, the system in which I do my most serious listening comprises an Onkyo C-7030 CD player, Legacy Audio StreamLine preamplifier, Legacy Audio PowerBloc2 amplifier, and a pair of Legacy Audio Focus SE speakers augmented by a Legacy Point One subwoofer. I also do a lot of listening while driving in my 2016 Acura RDX with its nice-sounding ELS Studio sound system through which I play CDs (the ones I especially like I rip to the Acura's hard drive so that I can listen to them whenever I want) or stream music through the system using my LG G7 ThinQ cell phone, which features surprisingly sophisticated audio circuitry. For more casual listening at home when I am not in my listening room, I often stream music through the phone into a Vizio soundbar system that has remarkably nice sound for such a diminutive physical presence. And finally, at the least grandiose end of the scale, I have an Ultimate Ears Wonderboom Bluetooth speaker for those occasions where I am somewhere by myself without a sound system but in desperate need of a musical fix. I just can't imagine life without music and I am humbly grateful for the technology that enables us to enjoy it in so many wonderful ways.
Bryan Geyer, Technical Analyst

I initially embraced classical music in 1954 when I mistuned my car radio and heard the Heifetz recording of Mendelssohn's Violin Concerto. That inspired me to board the new "hi-fi" DIY bandwagon. In 1957 I joined one of the pioneer semiconductor makers and spent the next 32 years marketing transistors and microcircuits to military contractors. Home audio DIY projects remained a personal passion until 1989 when we created our own new photography equipment company. I later (2012) revived my interest in two channel audio when we "downsized" our life and determined that mini-monitors + paired subwoofers were a great way to mate fine music with the space constraints of condo living.

Visitors that view my technical papers on this site may wonder why they appear here, rather than on a site that features audio equipment reviews. My reason is that I tried the latter, and prefer to publish for people who actually want to listen to music; not to equipment. My focus is in describing what's technically beneficial to assure that the sound of the system will accurately replicate the source input signal (i. e. exhibit high accuracy) without inordinate cost and complexity. Conversely, most of the audiophiles of today strive to achieve sound that's euphonic, i.e. be personally satisfying. In essence, audiophiles seek sound that's consistent with their desire; the music is simply a test signal.

Mission Statement

It is the goal of Classical Candor to promote the enjoyment of classical music. Other forms of music come and go--minuets, waltzes, ragtime, blues, jazz, bebop, country-western, rock-'n'-roll, heavy metal, rap, and the rest--but classical music has been around for hundreds of years and will continue to be around for hundreds more. It's no accident that every major city in the world has one or more symphony orchestras.

When I was young, I heard it said that only intellectuals could appreciate classical music, that it required dedicated concentration to appreciate. Nonsense. I'm no intellectual, and I've always loved classical music. Anyone who's ever seen and enjoyed Disney's Fantasia or a Looney Tunes cartoon playing Rossini's William Tell Overture or Liszt's Hungarian Rhapsody No. 2 can attest to the power and joy of classical music, and that's just about everybody.

So, if Classical Candor can expand one's awareness of classical music and bring more joy to one's life, more power to it. It's done its job. --John J. Puccio

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"Their Master's Voice" by Michael Sowa

"Their Master's Voice" by Michael Sowa