Yes, there's a lot of slang/jargon to navigate. I'm assuming you play guitar... preferably electric guitar which would make it easier? Just keep in the back of your mind that the jargon used by guitarists and electronics engineers (EE) and legitimate field techs is not the same - not even close. In fact, guitarists are the biggest pain in the ass when discussing amps, pedals, guitars, cables, etc,. (and I can say this as a guitarist over 30 years). In fact, I was playing guitar before I received formal education, and it was a painful realization of accepting how ignorant I was, yet somehow still explaining it correctly about 50% of the time. So keep in mind that the glossary of terminology you learn as an EE is the correct in definition and context, and about 50% of the jargon you hear guitarists use is either completely wrong, or correct wording used completely out of context - yet somehow will still make sense to nearly 100% of guitarists. Here's an example of what I mean - a post about "gain" by a guitarist.

Now clearly, we know this "guy" (I can't imaging a woman wanting to write this style of drivel - they have their own style of drivel) is not formally educated - or even the autodidact type who is remarkably self-educated. In fact, he hasn't even bothered to look up "gain" in the dictionary, because he'd discover there are several types of gain - voltage, current, power, antenna, and laundry detergent. This is the true guitarist whose inspiration is free and not not hidebound by the laws and physics that occur in electronic circuits. He really doesn't want to know all the specifics of electronics as it could interfere with his being cool. He has acquired his own understanding of what happens as the guitar signal (or "toan" as he would say), travels from the guitar, through his pedal board, and into his amp to the speaker. Even though everything he is saying sounds like drivel among electronics techs and engineers, he is using a form of vernacular that works well among he and his friends - not to mention the sales people largely responsible for the dumbing down effect. Now I know I'm probably sound facetious or sarcastic, but not at all. Even though he's got most of it all wrong scientifically, he is making sense to fellow guitarists. Over time, you'll realize that when he says, gain he means "more loud" - and by that he means "good" more loud and not "bad" more loud, which will include additional adjectives to help you, like: muddy, flat, stale, or sterile. It doesn't matter which adjective he uses, they all mean the same thing - "Bad" more loud. So, getting the idea?

Now in tube amp theory, you won't have to worry about language that makes absolutely no sense. In fact, if you notice, my comments are free of that guitarist vernacular I just mentioned, it was the other dude who used the term "stiff" (and to be truthful, I'm not entirely sure what he means, but I know what he's trying to get at). This phenomenon referred to as "Sag" is a touch and feel kind of effect that's very difficult to describe, but imagine hitting a power chord aggressively with the amp cranked to the point of distortion. With a tube rectifier, you'll get a kind of delayed swell of distortion that builds over a few milliseconds then hangs on as the power supply current attempts to stabilize. A bridge rectifier responds immediately, and so the argument (among both techs and guitarists) is whether or not that genuine sag effect can only be created by building a tube rectifier into the circuit. In the case of the Mesa Road King, Mesa has both power supplies with a switch so the guitarist can choose either the solid state bridge diode power supply, or tube rectifier. So, clearly, Mesa has engineered an amp that provides either/or. So, when the other gentleman referred to stiff, it's one of the "guitarist" feel descriptors that tries to articulate the immediate response of a power chord from an amp without a tube rectifier circuit, and also the ability to use a solid state circuit PS simulate the "spongy" sag effect by altering the capacitor values in the filter stage.

Still, all this yammering aside, don't let it worry you. The important thing is you'll learn a great deal by building any amp, but particularly getting your head into a tube amp. The reason I recommend the Fender 59 Bassman 5F6A is because there is probably no amp more famous (the inspired forerunner of the Marshall Blues Breaker and the later Marshall Plexi series of the 70s), more interesting to learn from, and few better amp circuits as forgiving to tinker with and modify after you build it. So, just my 2 cents. Hope that helps! ;)