For those who may not be familiar with the term, a "tube amp" is short for a vacuum-tube amplifier. Many people know that before the transistor were invented in 1948, the only way to do electronics was with vacuum tubes. By the 1960s, most electronics used transistors or integrated circuits, but tubes are still used to this day in a few niche applications, notably the music industry. For reasons that have to do as much with esthetics and culture as with technical factors, vacuum-tube guitar amplifiers play a role in rock music similar to what Stradivarius violins do in classical music. And some people of a certain age who recall the days of the 1950s when a home stereo system required a big, heavy, hot vacuum-tube amplifier still think tubes sound better than transistors, or at least look better, with their filaments giving off a warm orange glow.
So there is a market today not only for vacuum-tube guitar amplifiers and vacuum-tube microphones, but for vacuum-tube home stereo amplifiers as well.
Over a decade ago, for both professional and personal reasons, I built a 1950s-style vacuum-tube stereo amplifier from scratch, using plans I found online. The parts alone cost on the order of $200 or more, and if I had charged somebody for the fifteen or twenty hours of labor I put into it, at my going consulting rate I would have had to charge in the mid-four figure range if somebody had wanted to buy it. And specialty high-end custom manufacturers still sell what I'll call genuine vacuum-tube stereo amplifiers similar to the old McIntosh or Harmon-Kardon models, but they do cost several thousand dollars and up.
Well, along comes a company I'll call Stonetown, advertising a "vacuum tube amplifier" for the low price of $160. And a friend of mine I see frequently buys one, and installs it in his office where we have a sack lunch together. He hooks it up to an FM receiver and a couple of speakers, and we enjoy listening to the local classical station while we eat. It's a cute little thing: brushed-aluminum front panel, a little analog VU meter that jumps up and down with the music, and four little miniature-style tubes on top inside vaguely Art-Deco symbolic metal ring shields that mainly keep you from knocking the tubes over. And behind the tubes is a big square plastic box that I naturally assume encloses the necessary output transformers. Tubes are inherently high-impedance devices (high voltages at low currents) and because speakers have low impedance (they need lots of current at a low voltage) you have to use big, heavy iron-and-copper transformers in vacuum-tube amplifiers that drive speakers.
My friend has used this amplifier for the last couple of years. It worked fine until last Tuesday, when the left channel went out. We swapped speakers and input cables to make sure it was the amplifier and not the receiver or the speaker. Then I said to him, "Look, we're electrical engineers. Let's take the thing into the lab and see what we can do about troubleshooting it."
He was game, so he unhooked the thing and I picked it up to take it down the hall to his lab. When I lifted it, it seemed rather light for a product that was supposed to have a lot of iron and copper in the transformers. But as I set it upside-down on the workbench, I reminded myself that at least part of it was solid-state, because it had a USB input for digital audio, and I don't think anybody has ever built an all-vacuum-tube USB decoder. So there had to be some solid-state electronics inside, but maybe just enough to create the analog signal for the tube-amp part.
We were in for a surprise.
When we got the thing apart, here's what we saw. There was a transformer, but it was inside the main chassis, and it was a quite ordinary inexpensive power transformer of the kind you would use for a solid-state amplifier, not a tube amp. That was because nestled close to the front panel was a little circuit board about four by six inches with a complete solid-state stereo amp on it, all the way to the power transistors on heat sinks inside the chassis.
What about the vacuum tubes on top? Well, we could see a small cable that apparently did nothing but light up the tube filaments. There were not enough connections we could see that would be necessary if the designers had used the tubes for anything more than window-dressing, or should I say amp-dressing.
And that big black alleged transformer on top? Empty. Just a hollow plastic box with air slots on back to let air circulate to the heat sink below it. You could call it a chimney, maybe, but it wasn't enclosing anything but air.
The whole thing reminded me of a scene from Mark Twain's The Adventures of Huckleberry Finn. Huck travels for a while with a couple of fraudsters who put on a mildly obscene show for a hick town in Arkansas, which is nothing like what they advertised it to be. Just before the audience rises up to pelt the performer with tomatoes, they shout, "Sold!" Meaning roughly, "You sold us a bill of goods."
My friend is capable of getting mad, but when we realized what the deal was, he just grinned ruefully and said, "Well, I should have known better than to think I was getting a real tube amp for $160, when the next cheapest one is $2500." What made it worse was that an officemate had seen his and bought one for herself. We went back and told her the story, and she just laughed.
So here's the ethical issue: is Stonetown guilty of false advertising? I went back and looked up some of their ads. They call it a "tube amplifier," and say it's a "[c]lassic tube amplifier, modern features," and so on. I suppose you could say that it's up to the designers as to how much they use the tubes in the amplifier. But lying can be by implication as well as by flat statement.
This experience can be summed up in the Latin motto Caveat emptor—let the buyer beware. If it's too cheap to be believed, don't believe it. And if we hadn't opened the thing up last week, we might still be enjoying the illusion of having a genuine vacuum-tube amplifier at a solid-state price. As it is, we're a little sadder, but a lot wiser.
Sources: As I'd rather not be sued for libel, the real name of the company does not appear in this blog. But from online comments I've found, they are not the only firm that engages in this type of thing in the so-called tube amp market.
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