I found my mother’s old, but up to date at the time, textbook: Theory and Applications of Vacuum Tubes.
Most people can read and understand Shakespeare. Chaucer’s pushing it, unless you deal with historical literature.
Incomplete and basically wrong as the comparisons are, my question is similar. Are the mathematics as presented in the book via “tube-thinking” so foreign that it is difficult to follow the book (read it) at all?
Leo
Not only is it still understandable,to a lot of people it’s still relevant. A lot of audio aficianados like the amplification profiles of some vacuum tubes more than those of solid state. (It doesn’t even matter if the newer ones are more accurate – it’s some quality of the old vacuum tube frequency response they like.)
In addition, vacuum tubes are a lot less subject to EMP. One thing that surprised them when they examined a MiG many years ago wads how it still used vacuum tube technology. There might have been a reason for it.
But the basic rules of EE and its nomenclature is still the same. Heck, the devices are often the same. I was stunned to learn that Operational Amplifiers (Op-Amps) started out as vacuum tube devices – if ever an electronic device looked as if it originated on a silicon chip, that’d be it. But it long predates semiconductor technology. Of course, there’s the trade-off. When I first saw a vacuum tube op-amo, it took up a whole drawer of electronics. Even forty years ago, you could fit two of them on a chip smaller than your fingernail. Now they’re microscopic.
people that understand analog electronics for things like amplification, control could understand them. there is different infrastructure to understand.
Back in 1950 there were op/amps that were roughly cubes about 2 inches on a side. The ones I dealt with (they were old in 1955) used a pentode and two triodes, all subminiature. The pentode had an unfedback gain of about 2000. One of the triodes was used as a cathode follower. They tubes were very flaky, but in circuits that were essentially 100% fedback, it didn’t matter much. There were also some resistors and maybe a capacitor. They were the heart of a very large electronic analog computer.
I have my grandfather’s antique electronics books from the late 1930s (reprinted in 1945), the Audel’s Electric Library series. The electronic schematics are quite understandable, though a little of the terminology and some of the symbols are archaic. They use “cycles” instead of hertz, and “μμf” (micromicrofarads) instead of pF (picofarads), for example.
My entire training on vacuum tubes consisted of 3 class periods in college, and I’m not exactly fresh out of school (that was 25 years ago). I don’t know if it is taught at all these days. I do know the basic principles involved though, so I can usually muddle through a book on tube circuits.
A lot of the principles are the same. Transistors can be used kinda like electronically controlled switches, where their output is either on or off, and tubes can be used the same way for control. Transistors can also be used as amplifiers by varying the current and keeping the transistor in a region where it amplifies the signal. You can do the same sort of thing with tubes as well.
Some circuits even have very close equivalents.
For example, here is a push-pull tube amplifier:
http://www.aikenamps.com/PP.gif
And here is a push-pull transistor amplifier:
http://www.tpub.com/content/neets/14180/img/14180_41_2.jpg
Even someone who doesn’t understand circuits should be able to see that they are very similar.
I could read through a book and understand it, but I wouldn’t be all that comfortable just jumping in and designing my own tube circuits. I could probably do it if I had to, but it’s not something that I have any experience at.
Just for giggles, I searched through the first page of google books that had a preview available and looked through them. There were a few basic theory books like the one in the OP, and I had no trouble at all understanding anything I saw in those (I just quickly scanned through them though). In a book about tube circuits for wireless communication I did see an entire chapter on how to tune the plate current in a tube circuit. I could understand it easily enough, but there was a lot of info in it that I had no experience at all with, like some practical information about how to reduce hum in that kind of circuit. They tend to use coils all over the place, where we tend to avoid coils in modern circuits due to cost, size, and manufacturability reasons.
The terminology in some of the books is a bit archaic, but I’ve heard those terms being used before so I could understand it. The math wasn’t foreign at all. It’s the same math and similar principles to what we use in modern circuits. It’s mostly that the implementation is a lot different.
Yeah, I do have many triode followers.
that’s something to beam about.
Math should be easy. Maybe not schematic symbols, but a quick study should rectify that. Ha, I said rectify.
I’m not much fresher out of college, but by the mid-1980s our EE courses did not mention vacuum tubes at all (even the radar course) - instead it was all transistors, ICs, and especially the newer kid on the block at the time, the MosFET* - op-amp design was assumed to be using transistors, not tubes (we loved circuit designing using op-amps - infinite input impedance and zero output impedance made calculations easy).
At the time, I read on my own some books from the 1960s about EE which did feature Vacuum tubes, and remember getting the impression that each additional grid in a tube (e.g. triode → tetrode; tetrode → pentode etc) was added in an attempt to fix a problem introduced with the previous grid; e.g. the tetrode grid was added to reduce capacitance between the anode and the triode control grid; the pentode grid was introduced to suppress the secondary emission issue caused by the tetrode grid, and so on) I know better now, but still I was glad tubes were on the way out (don’t recall if the tube-testers in the local Woolworths where gone by then, though 
)
Finally, why do some musicians feel tube amps are better than transistor-based amps anyway? Even back in the 1980s there were power FETs and such capable of handling the range of amplifier tubes w/o distortion. I could see a case when people complained about analog vinyl records vs digital compact discs, but both tubes and transistors are analog (the circuit designs determine if analog or digital usage) - is it the distortions introduced by the inherent nature of the vacuum tube itself? (Whee! Shoot electrons emitted off a heated up wire toward a postive plate, and use a grid in between them to more or less control the magnitude of this electron beam - and then add some more grids to compensate for whacky secondary effects. What could possibly go wrong?)
*Newer kid is relevative - FETs date back to the 1920s, it seems - perhaps our EE course instructors were embellishing a bit back then…
For a guitar, tube amps do sound better. A “clean” amplifier that doesn’t distort the signal at all works great for a bass guitar or a keyboard, but it makes an electric guitar sound like crap. An electric guitar sounds MUCH better through an old tube amp. The type of signal distortion you get just happens to make the sound of the guitar much more pleasing. I have a digital effects box that emulates several different tube amps so I can get the same effect without trying to keep an old tube beast operational.
There are some audio snobs who believe tubes are just better, but these are the idiots who buy monster cable and think that it improves their sound. Some people just want to believe that you have to spend huge amounts of money to get good sound.The only valid point these people have is that vinyl does reproduce very high frequencies better than a CD. Most people though are physically incapable of hearing the difference. But if you are one of the few people who can tell the difference (i.e. you can hear those “mosquito” ring tones) and you really have a thing for piccolo music, then maybe you’ve got a point. Other than that, analog recording sucks. It’s a constant fight against noise and distortion and media that degrades every single time that you play it.
Actually getting someone to try to specifically describe, let alone quantify the improvement of any one piece of musical amplification equipment over another is really difficult. You get terms like “livelier” “warmer” and my favorite, “more organic.” To be fair to musicians, when you have an artform that assimilates the disparate sounds of hundreds of musical instruments, and has to accomodate room acoustics in real time, if you have the talent it is probably easier to do the thing than it is to describe the thing.
The difference between some amp squeaking long hair wannabe on an overpowered speaker system and Jimmy Hendrix actually playing the feedback on his guitar by moving it in and out of range of the speaker, live in front of thousands is not a scientifically definable quality.
And if you think your tube amp makes you sound better, you may well play better because of it.
Tris
Very unlikely.
I’m an EE. I got my BS in 1992, and we didn’t study vacuum tubes at all. Took two semesters of microelectronic circuit analysis (i.e. linear and switching transistor circuits) and a semester of solid state physics (i.e. physics of semiconductor diodes, bipolar transistors, and FETs). Also took a semester on CMOS switching circuits when I was a senior.
I work with a number of young EEs fresh out of school, and I am amazed how little they know about analog electronics. Sadly, I don’t think the EE programs place much emphasis on that stuff anymore. Seems most of their classes were on modeling, signal analysis, programming, etc.
Read this thread.
I remembered an old antenna company I was loosely associated with the other night and started looking for into on it; I ended up following links to early RF design articles and even early frequency control companies. Along the way, I bumped into quite a few circuit schematics where tubes were used, especially oscillator circuits because that was my old profession-----these things went back to the time when 10.0 MHz oscillators were considered to be the high frequency limit. Thank God for solid state electronic devices; I had forgotten how headache inducing tube circuits could be. We used to add inductors (we called them coils) to lower output frequencies when we miscalculated load capacitance and then go insane over why the stability went to hell. Damn, those were the bad old days and now I’ll have another night of bad dreams.
electronics can never be fully digitized as long as people use them.