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Since no book review would be complete without some nitpicking and grumbling, I will not disappoint you. But first, I would have liked to provide another quote from Johnson, but I could not find it. The gist of what the dear doctor said was that the writer of essays blog posts also count has a much easier time than the writer of a thick book does, as shorter piece of writing exempts the writer from encountering logical inconsistencies and plain bone-head mistakes that are implicit yet hidden in his short work, but which would be revealed in a longer work.
Moreover, reviewing is much easier than creating. This reminds me of what I wrote back in blog number : I once had lunch with an audio magazine editor. He told me that he gets several offers a day by eager audiophiles who want to write audio product reviews. But if someone can write a decent article on how SACDs are mastered or the history of some great recordings or explain how Thai audiophiles are different from Chinese or Japanese audiophiles, then I am very interested.
The power of invention has been conferred by Nature upon few, and the labour of learning those sciences, which may by mere labour be obtained, is too great to be willingly endured; but every man can exert such judgment as he has upon the works of others; and he whom Nature has made weak, and Idleness keeps ignorant, may yet support his vanity by the name of a Critic.
Idler No. He covers the the two generic, single-triode circuits, the cathode follower and grounded-cathode amplifier, but not the grounded-grid amplifier or the inverted amplifier aka grid amplifier , wherein we use the grid as a "plate" and the plate as a "grid.
He even covers the Aikido cathode follower, but gets the design example slightly wrong. See blog number Assuming that the input signal is noise free, say a CD player or DAC or tuner in other words, an external signal source , then the following arrangement works well. Because both triode share the same cathode resistor value, the ratio between the power-supply-noise voltage divider resistors is simple: the top resistor should be mu - 1 times bigger than the bottom resistor.
Practically, however, we get the most bang per microfarad by moving the null center only down to twice the wall-voltage frequency, so Hz in America and Hz in Europe.
But, John, your version presents an output impedance of ohms, whereas his version only presents ohms. But just how low an output impedance do you really need?
If you are willing to accept a higher idle current, the two cathode resistors can be lowered to ohms. Remember that the cathode resistors perform three tasks: they set the idle current, they linearize the triodes, and the top resistor protects the cathode follower from capacitive loads.
If you are willing to forgo the last two features, another approach would be to eliminate the top cathode resistor and bypass the bottom cathode resistor with a big capacitor. If the output impedance needs to be something close to zero, then solid-state gear is the better answer. And if the load is a brutally-low ohms, the impedance of many fine German headphones, then a push-pull output stage is needed, such as the following. The above is a complete tube headphone amplifier for ohm loads.
As the White cathode follower has gotten my full Aikido treatment, the above circuit not only delivers big symmetrical current swings into the ohm load, the PSRR is exemplary.
Note that the ratio between the power-supply-noise voltage divider resistors has changed. See blog number for more details. What if you do not want a complete headphone amplifier, but only a White cathode follower stage?
The result is equal current swings from top and bottom triodes and excellent PSRR. Returning to Designing High-Fidelity Tube Preamps, the second minor grumble I could make is that the list of tubes that Merlin highlights is a tad too short.
I would like to see him cover some sleeping beauties, such as the 6SU7, which is a 6SL7 but with tightly matched triodes. Or the and , which are late-development dual triodes which are largely immune to cathode-interface problems. Nonetheless, my complaints are few and small. Merlin Blencowe has written a fine tube-focused book. Buy it. What is the Best and Easiest Method of Studying?
A great question; yet it is one that is so seldom asked. Note the oddity of the situation: we spend a huge chunk of our life in school, trying desperately to learn, but we are seldom taught how to learn. When I was in college, I devoted much of my time to learning how to learn. Because I knew that the time I saved would be mine to waste, I became fiercely good at it. For me, offense was much better than defense; active over passive.
For example, before cracking open a textbook, I made a long sometimes woefully short list of all that I already knew about the topic. I also listed key items that I expected to encounter, such as, What type of government was there, republic or monarchy? What is its history? Who are famous people who were born there?
What are its borders? What does it produce? Then, as I read the book about Liechtenstein, I would place a check next to items in my list that I had found and write down the answers to the questions that I had asked myself. If the topic was something conceptual, such as psychology, I also listed key items that I expected to encounter, such as, What is the definition of the topic or field of study?
Who are the greats within it? What is its strict purview? What other studies overlap with it? In other words, I never read passively; instead, I read aggressively as a hungry wolf in search of prey.
Or, say you wish to read any difficult book well. Here are some quick tips: make the list of key items that you expect to encounter. The more you can write down, the more are likely to learn and retain. Next, skim and glance through the entire chapter, paying attention to all the subheadings and illustrations and graphs. When looking at a graph, be sure to trace the plots with your finger or pencil point, as the physical act will help burn the plot in your memory. Now, start reading.
Once you are done, skim over all that you have just read and re-read the summary or last section. Two or three hours later, quickly go over the chapter again. Never highlight as you read, as you do not yet know what is important—i. After you have read the chapter, you can go back and underline what is truly important. Whenever you get one of those "Oh I get it" moments, stop studying and go outside and walk amongst greenery for ten minutes or so before going back to studying.
Your brain needs time to consolidate what it has just apprehended. Before going to sleep, quickly review your notes or skim through the chapters that you read earlier. One psychological problem I encountered was my dread when confronting a super-thick textbook. My solution was radical: I cut the fat book into chapters, with a kitchen knife. Instead of a single fat book filled with 1, pages, I ended up with 30 thin chapters, each only 40 pages long.
Yes, slicing a book up is a sort of desecration, but I took some comfort in the belief that the textbook had it coming. I like to read in bed. Although I am a big brute of a man, I hate heavy books, preferring many thin books to one fat monster. Computer books are the worst offenders.
The key point is that most students view their workload as hurdles that they must clear before moving on to the next one; and once cleared, to be forgotten as quickly as possible. In sharp contrast, I viewed my required studies as poorly-prepared, nearly-inedible, unseemly-looking food that I had to chew over and over again before I could digest it fully, much like a cow eating grass. Education has been defined as casting fake pearls before real swine. We are not in control of the first half of that definition, but we are in control of the second half.