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Home » xyzzy » Dungeon » The Blind Leading the Blind
| Re: The Blind Leading the Blind [message #77663 is a reply to message #77654] |
Fri, 30 August 2013 20:17   |
Thermionic
Messages: 208
Registered: May 2009
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Master |
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I used to get that same thing, Bruce, and it really chaps my backside. Some of these people don't know the first thing about how a tube circuit works in the first place, but they'll always believe it's their mission in life to prove you wrong, using information from equally inexperienced and ill-informed self-proclaimed "gurus" (who shall remain nameless, as most have far larger legal teams than I do).
I've personally chatted with some highly regarded "tube amp gurus" whose names were spoken in reverent, hushed tones by many, that didn't know the first thing about the concept of separate AC and DC conditions, much less how the tube uses them to produce an increased amplitude copy of the input signal across its load. They didn't understand mu, Gm, and Rp and how they interact in a triode, let alone how a beam tube or pentode works. They didn't know anything about how to design a simple grounded cathode stage, much less something like a LTP phase inverter. They were completely clueless about impedance, reactance, slew rate, Miller Effect, operating class, load lines, etc, because everything they do is strictly by the seat of the pants, through trial and error. What they did know was plenty of wive's tales, urban myths, and voodoo hoodoo, like:
The only good sounding output transformers have kraft paper bobbins and interlayer insulation, not synthetic materials like nylon, Kapton, Nomex, Teflon, etc.
Only amps wired with vintage-type waxed cotton wire can sound good.
All capacitors, resistors, etc, of the same value sound the same, because they measure the same with a handheld DMM.
The correct way to adjust the bias of a grid-biased amp is ________ (fill in the blank here with any one of around ten incorrect methods).
If it's grid biased, it's Class AB. If it's cathode biased, it's Class A.
This is a very short, abbreviated list, that I could add to for at least an hour. I'd say that for every truth you read or hear, there are at least ten falsehoods out there. One of the worst places this happens is in the guitar amp realm. Example: several years ago, I went into a music store and noticed there was a blackface Fender Princeton sitting on the bench in the back. The guy said he'd just recapped the power supply, then started talking some of the craziest stuff I've ever heard. I kept quiet, smiled politely, and didn't say anything until he said, "Did you know you should always bring even brand new caps up on a Variac to form them up?"
Having been asked a direct question and expected to respond, I did. I explained how electrolytic caps are manufactured with pre-formed foil (or else they would be dead shorted, duh!) and then "repair formed" before leaving the factory, by having a voltage applied to heal up any spots where the oxide film was damaged when the foils were wound.
His brow furrowed, his nose wrinkled and his lips curled downward. He rather huffily let me know I was wrong, because a certain "guru" had said it in one of his books, and that I needed to get his book so I could learn how to do things "the right way." He then mentioned two other "gurus" and their books, that he obviously regarded as the greatest masters of the tube amplifier who ever lived. These three particular "gurus" are the three most hated men on the face of planet Earth by your highly knowledgeable, old school "real deal" guitar amp techs. The reason is that those three men have spread more nonsense and foolishness about tube amps than all the others put together.
One of these three stopped by a friend's music store several years ago. He was wanting my friend to take on a dealership with him, and had some of his amplifiers on hand. My friend noticed on the rear panel of the amp that the rated power output was only a few watts, so he asked if it was a Class A amp. Mr. Guru replied, "Oh yeah, it's Class A all the way. Everything in it is the best stuff money can buy."
Yep, Mr. Guru didn't even know what Class A operating class was! My friend was dumbfounded to the point of silence. He paused a bit, then began to pick Mr. Guru's brain to see just what else he didn't know. Turns out, Mr. Guru didn't have the first clue about how tube amps even worked, even though he has a very well known book on tube amps ascribed to his authorship! The book is chock full of misinformation and incorrect tech info, but more than anything else it's laden with advertising hype for his bogus products. Still, nearly every guitar amp tech has it (even the good ones) because it contains tons of cool old amplifier pics and a comprehensive library of vintage amp schematics. But, there's still way more knowledge in it than Mr. Guru had, and my friend later found out the name of the person who had actually written the book.
This "guru" is a self-proclaimed "defender of the faith" when it comes to tubes, and is credited as one of the men who saved the tube amplifier from its demise. Truth is, just before he started his company, he'd worked as head of sales and marketing for a company that made only solid state amps, and adamantly proclaimed the vast superiority of their solid state bass guitar amps to a main competitor's tube bass amps, which BTW are still regarded over 35 years later as among the best sounding bass amps ever made. And, 35 years later, his own company's amplifiers are still regarded as some of the worst.......
He also once claimed on a forum that the critical ingredient behind the highly coveted guitar tone on a certain album was special tubes bought from his company. The problem with that is the undeniable fact that the album was recorded around two years before Mr. Guru ever started his company, back when he was with the solid state amplifier company.......... AFAIK, he has not made this claim any more, after several people caught him in the lie and spoke up.
Like the other two, this guy's a quack when it comes to tube circuits but a master at deceptive marketing. Well, maybe they're not exactly masters....I had to laugh when I once saw the schematic of another one's particular amplifier model, that was an original vintage Fender schematic with no changes made whatsoever except that the Fender name and model had been removed and replaced with his!
Myself, I must've had a hundred guitar players tell me they want me to do such and such to their amp in such and such way because they read it in one of those guys' books. My response is always "If you don't think I know what I'm doing, then why did you bring it to me? You need to take it to somebody else." AAAARRRRRRGGGGHHHHH! 
Thermionic
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