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Used to be, tubes were the only way to electronically make pictures and sound. Just like horses were the only means of personal transportation. Untold billions of them were made, and no doubt many of those make up the underpinnings of many a landfill. Thousands probably are at the bottom of the ocean in sunken ships (most likely still in perfect working order), and hundreds have even been shot into outer space (and of those still up there, most probably still work also).

Then along came the discovery that tiny chips of germanium and silicon could make electrons behave the same way as inside a vacuum tube, only with less current, less heat, smaller size, longer life, etc. The transistor started a plunge towards the microscopic, became the parent of the integrated circuit, which fathered the microprocessor, CPU, DRAM, CMOS, EEPROM.....you need a score sheet to keep them all straight. Except for image CRTs, tubes were largely forgotten.

Until now. Over the last several years, vacuum tubes are glowing again. In high priced, mostly hand built audio systems, in the military (where they can survive the electromagnetic pulse of a nuclear blast), in high current industrial equipment, and in the trend towards restoring and using antique radios, TV's, and hi-fi gear. Most radio transmitters have always needed tubes, and now ham operators are restoring and using tube gear like never before. Audiophiles, some of whom never abandoned tubes, are now becoming tubeheads. Tubes image better, have a smoother high end, soft clip at output extremes which merely adds harmonics instead of blowing up your speakers, and are user replaceable. Some of the popular audio tubes are being manufactured again, and some of the Russian versions sound pretty good. Enough of the other types escaped the dumpster to last us tubeheads into the foreseeable future.

So let's talk tubes! I collect, use and sell tubes. I have been fascinated with them ever since my preschool days. I remember the TV repairman coming to our house with his tube caddy, jammed full of colorful boxes of tubes, working inside our 1950 RCA (also jammed full of tubes). My father and grandfather also filled in for the repairman on simple fixes. What fun for a protogeek to go along to the corner drugstore with all the TV tubes to test them on their huge tester! The fascination felt when peeking through the holes in the back of the old radio and seeing the orange glow of the glass tubes!

First of all, transistorized equipment can and does sound as good as tube equipment. It just takes a very expensive transistor amp or radio to sound as good as a very simple tube unit of the same type. For restoring antique electronics, tubes are a must, period. I may be a tubehead, but I enjoy and recognize good transistor equipment, too. The first premise of this hobby is to think for yourself. Let your ears be your guide. Duke Ellington said, "If it sounds good, then it is good!"

2. Older tubes are often better. The large plate audio output tubes, like the 2A3 and the 45, are in demand. In the right design amp, they sound fabulous. You don't need megawatts of output to sound good in a tube circuit. Just efficient speakers.

3. More praise about older tubes: The cathodes of the pre 1960's tubes were coated with more emitting material, and were better made. With a ruggedized design, such as GTA and GTB types, these tubes will last a very long time in use.

4. Some people have a strange aversion to used tubes, like vampires avoiding silver and garlic. My answer is see number 3 above. A used older tube is probably better than a new old stock version made in the 1970's. When I sell used tubes, I sell with confidence, since I test every tube I sell. Often my used tubes test as good as new old stock on emissions. Some antique tubes are so rare, that used is all that is available. For an antique radio which is seldom turned on, retubing with good used tubes can be easier to do than hunting down all new old stock versions. The radio will sound as good as with new tubes, anyway. Don't let anyone tell you used tubes are junk.

5. Contrary to popular belief, a tube with low emission is not necessarily bad, especially an audio output tube. In particular, I have compared unmatched 7591 output tubes with low emission to new old stock 7591A's, matched and with good emission, and heard very little difference. I know I'm going to get flaming e-mails about this, but again, I know what I heard. I have been an audiophile since 1968, a location sound engineer since 1969, and an audio/video tech since 1978. I think I can say I have trained ears. The bottom line is, keep the low emission tubes you are swapping out as spares. You may need them as tubes become harder to find! Of course, an RF amp tube, a rectifier, a detector, or an IF stage tube with low emission will degrade the performance of your set and should be replaced.

6. The 12AX7, a tiny tube we all seem to either love or hate. It seems to be getting as much attention as Western Electric 300Bs these days. This tiny triode is found in many amps, preamps, guitar amps and microphone preamps. Some say it sounds mushy, I say it sounds great. True, it is not as quiet as the 12AT7, but I have heard some mighty clean, well defined music through these babies. In the wrong circuit it probably does sound terrible. Why do you think they use 12AX7s in guitar amps to get that oversaturated, overdriven sound? It saturates like no other tube. In a preamp circuit where it runs near saturation, it probably does sound mushy. Overdriven, it can sound like Jimi Hendrix on a bad day. Hence it's popularity with the Stratocaster playing tube rockers. It has it's place in tube mic preamps as well, with it's signature tube warmth it adds when driven at levels below saturation. Driven in the midpoint of it's saturation curve, I hear clean musical articulation, tight bass, and sharply defined imaging.

7. Urban legends of the 12AX7, to continue a topic: Smooth plates are better than those with ridges. Tubes with two or four seams on top are better. The 7025 industrial version is better. A diamond crest or a cartoon tube blowing a bugle indicate better quality. RCA, Amperex, Telefunken, Brimar and Mullard are the only good 12AX7's, the rest are not audiophile quality. Only buy those with gold pins. Wow! No wonder this tube keeps getting more expensive every day. It's legendary! My thoughts? The 7025 is a tad quieter and built to tight specs and gold pins don't oxidize. I flat out disagree with which brands are the only brand to buy. I have heard Philco, Motorola, Tung-Sol, Raytheon, GE, Sylvania, DuMont, and whatever. While there are minor variations between brands, I'll take any of those 30 year old or older tubes, new old stock or used, over any of the Chinese, Yugoslav, or Russian versions made after 1978. As far as the other rumors go, let your ears be your guide. If you hear good sound from smooth plates, then it is good. You are the one listening!

8. The 6SN7 is probably one of the best bargains in audio triodes today. It sounds the best for all around hi-fi use, has lower microphonics, and was produced in huge quantities. Hence the low price. I have them listed as low as $3.00 each on my excess stock page. It does not need negative feedback, a necessary evil in some preamp designs. I would choose this type, or perhaps the miniature 6FQ7/6CG7 (another bargain triode) if designing my own preamp. The RCA, GE and JAN-Sylvania all sound good, but again, use your own ears. Other older US made brands sound excellent.

I'm running out of space and time. I'll toss in another two cents worth next time. Remember, all ears hear slightly differently, and reasonable people will disagree. Send me e-mail with some ideas for the next article!

Copyright © 1997, 2003, Brent Jessee Recording.

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