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How did you get into amp teching?

Discussion in 'Amp Tech Center' started by trxx, Dec 24, 2019.

  1. printer2

    printer2 Poster Extraordinaire

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    At first I did not care about Rob's site when he showed the signal path through a layout drawing. Years later was directed to his site and he is doing many a service with his site. I heard Uncle Doug's videos are of great value. I usually direct a new builder to AX84.com https://ax84.com/archive/ax84.com/p1.html

    The The P1 Theory Document gives a decent explanation if the circuit in a SE tonestack guitar amp. Things that helps out is a good understanding of Ohm's Law and voltages adding up in a loop as well as currents. Get a handle on Thevenin voltage source, current source. Tube related there are many old historical texts that do a good job of how a hifi amp works.

    http://www.tubebooks.org/technical_books_online.htm

    ---------------------

    Basic Audio, Norman Crowhurst, 1959 - Thanks to Keith Carlsen!

    This is a 3-volume set on, as the title implies, basic audio. The best introduction to tube hi-fi I've seen, the first volume starts with the nature of sound, and covers the basics of speakers and microphones. Volume 2 continues with amplification, covering the basics of amplifier design. Volume 3 covers a little more advanced topics like feedback, power supplies, and recording. If you're a beginner, READ THESE BOOKS!


    http://www.tubebooks.org/Books/crowhurst_basic_1.pdf
    http://www.tubebooks.org/Books/crowhurst_basic_2.pdf
    http://www.tubebooks.org/Books/crowhurst_basic_3.pdf


    http://tubes.nekhbet.com/pdf/ga699ac.pdf
    http://ken-gilbert.com/images/pdf/ga100ac.pdf
    https://www.tiffe.de/roehren/ga200ac.pdf
    http://ken-gilbert.com/images/pdf/ga300ac.pdf
    http://ken-gilbert.com/images/pdf/ga400ac.pdf

    Here is the list of pdf's, have a few above.

    Understanding Hi-Fi Circuits
    High Fidelity Circuit Design
    High Fidelity Sound Engineering
    Audio Classroom - Designing Your Own Amplifier:
    Part 1: Voltage Amplifier Stages
    Part 2: The Power Stage
    Part 3: Phase Inverters
    Part 4a,b: Push-Pull Power Stages
    Part 5: Feedback Amplifiers
     
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  2. Viejo

    Viejo Tele-Afflicted Silver Supporter

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    Aspen's book was a good source of schematics back in the pre-internet days. Imagine not being able to access Schematic Heaven and it's encyclopedia of schematics at the click of a mouse. It was also my first exposure to Fender Amp history back at a time when that knowledge was not readily available. Aspen helped awaken people to the what treasures those old amps really are
     
  3. trxx

    trxx Tele-Afflicted

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    I did some more digging around and ended up ordering the book, Guitar Amplifier Electronics Basic Theory by Richard Kuehnel. It looks to be better suited toward what I need at this point that any of the other books I have seen. I'll report back after I have a chance to work through it. Also still reading back on The Tube Amp Workbook.
     
  4. jhundt

    jhundt Doctor of Teleocity

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    does anyone remember a book by Jack Darr? That was the ONLY book I could find before Aspen Pittman published his book. I didn't even own a copy - I borrowed one from a friend and photocopied it page by page. I didn't copy the title page, so I'm not even sure of the name.
    I just looked in the shop and I still have it, along with my drawings and parts list for the first amp I ever built.
     
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  5. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I didn't read through all the responses, but several. I wanted a great tube amp but couldn't afford one. I started with a Mojo 5e3 small parts kit, but sourced the tubes, transformers, and speaker on my own. And then I built my own cabinet. Then I built a Tweed Princeton for a friend. Then another one for another friend. And I learned how to do 95%+ of it right here on TDPRI. I bought my first soldering iron for my first amp kit - no background in anything but woodworking, and at that point, it was just stuff I watched my dad do growing up. Learned it all online. I don't know how many amps & cabinets I've built since then. I love doing it.

    But, honestly, the term "amp tech" gets thrown around so much online, but they aren't that plentiful in smaller towns. Augusta is one of the biggest cities in Georgia. You have to ask around for a friend of a friend to find anyone who works on amps. And none of them do it as a career. I won't touch a PCB for anyone, never have even tried. A friend of mine who's about 20 years older is my go-to guy who I've learned a lot from the past 2 years -- he's an electrical engineer who does it on the side because he loves amps and music. He finally told the local guitar store not to call him anymore for anything with a PCB in it. There aren't any "authorized techs" around here. Just guys who spent enough time to mostly learn what they are doing, and do it long enough to get good at troubleshooting. I mainly do cabinet restoration and fixes around here. If I can't figure it out inside, I send them to John, and John sends anyone with a jacked up cabinet or hardware issue to me. But, neither of us call ourselves amp techs, just amp "enthusiasts" who know more than the average guy with an amp.
     
  6. rolandson

    rolandson Tele-Holic

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    Just type a chapter heading into google scholar and it may very well turn up the book.
     
  7. Cysquatch

    Cysquatch Tele-Holic

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    If we could get @robrob and Uncle Doug together with a type writer, I think we'd end up with one heck of a great book on the subject. Rob's site is most excellent for learning, with tons of really useful graphics.
     
  8. Cysquatch

    Cysquatch Tele-Holic

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    Do you know if John would be willing to take on an apprentice of sorts/free labor monkey? I'm in Grovetown and would love the opportunity to get more hands one with somebody who knows their business. I've got a decent understanding from the hours of reading, but hands on stuff goes a long way for me.
     
  9. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Ha. I'm just a few miles away in Appling. Shoot me a message and let's grab a beer sometime.

    Sent from my moto g(6) using Tapatalk
     
  10. BobbyZ

    BobbyZ Doctor of Teleocity

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    I ordered a copy a few years ago, it's a book I would've gotten more out of when I first started in the 90s. Some of it was copied into Aspen Pittman's book.
    The book I wish I would've gotten first was an old junior high basic electrolytics text book. Found it in a thrift store printed in the early '50s I'd guess.
    That book would have been great to read first because it was written for someone with zero electronics knowledge. I don't care how good you are at this now, we all started out not knowing anything. That book walks you through each part and gives you a basic idea how it works.
    I started with Aspen's book then a few other "guru" books in the 90s, then every old tube related book I could find.
    They all assume one thing, that you know the difference between a metal tube and a cap can, an electrolytic capacitor from a coupling cap, a resister from a diode.
    But you don't! Nobody is born knowing that.
    Had I had that one simple book first it would've saved me a lot of time.
    The internet is a blessing and a curse. Since getting it I've learned a lot but anyone can get a web page. So you can get bad info there too. "Gurus" that spout out misinformation drive me nuts! Not a big fan of the guys that copy readily available information on a webpage either. If you do that and give credit where credit is due, that would be fine. But they copy the Top Ten Mods for a Super Reverb out of Gerald Weber's book like it was their own and whatever. (Not sure where he copied it from?)

    Everytime this subject comes up going to school for it comes up too. When I started I was running an industrial coatings buisness, had a wife and kids and lived in Northern Minnesota.
    Had there been a night course on obsolete electrolytics near by in the winter maybe I could've gone. There wasn't! Might have found an electrician class but that's not even close.
    Also you don't need to be an electronics engineer to fix tube amp any more than you need to be a degree in automotive engineering to fix a car.
    Yeah I'm ranting here. :)
     
    Last edited: Dec 31, 2019
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  11. Whatizitman

    Whatizitman Friend of Leo's

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    I just bought Design and Construction of Tube Amplifiers. It's got enough theory to keep me challenged. An EE would probably not get much out of it.

    https://www.amazon.com/dp/0615291805/?tag=tdpri-20

    You gotta wonder why Robrob, MuchXS, Wally, and others are so giving of their knowledge on the subject, particularly for beginners. I would venture to say they may see it's less time consuming, but not any less profitable toward their own goals to either blog for free or hang out in the forums, than to publish, market and/or sell an edited book. That's just my guess.

    --------------------------------------------

    I'm not a tech. Nowhere close. I would like to get good enough at some point to be a tech. But I'm not banking my future on it. I'm a noob, and will probably always consider myself that.

    I think the biggest struggle for any writer of a tech manual would be to figure out how far to go back. It's a big learning curve jump to go from "this is an electron" to "this is how a load resistor works". At least it has been for me. Just how much should a writer spend on fundamentals?

    My experience is that I need several resources to fall back on at any given point in time. I'm not only very low on the rung of electronics theory knowledge to begin with, but I'm also a very slow learner. I need to revisit concepts several times and in several ways before anything connects. And even then, I'm still probably wrong.

    This is more or less what my path has been. If any tech writers feel it helpful to see how one noob goes about trying to learn this stuff, great!
    ----------------------------------------------------------------------------------------------------

    I had Aspen Pittman's book way back in the early 90s. And while I learned a lot about amps from it, I really couldn't take in much practical theory. I didn't really delve into any amp repair or modding until years later, just following some internet tutorials. And even then, it was not until about two years ago that I really decided to dive in head first. I've purchased a book or two. But really, the internet has been my main classroom. I prefer books. But nothing compares to being able to have multiple references open at the same time.

    Before I could do anything beyond resoldering a couple of wires according to a tutorial, I needed to absorb some circuit theory fundamentals far more than I had until that point.

    https://www.allaboutcircuits.com/textbook/direct-current/chpt-1/electric-circuits/

    Really. That's the place I was at not too long ago. And to be truthful, not too much from that now. I have no engineering background. I'm a liberal arts major, many times over. But after many years without a tube amp, through good fortune I suddenly found myself with a SF Champ that was in need of repair. The internet seemed to agree that it was a good starting point for learning about amp repair and building.

    Googling brought me to TDPRI as well as Rob Robinette's site.

    After some study it became clear to me that the best beginner-ish resource is Robrob's site, particularly these pages. I continue to refer to them, a lot.

    https://robrobinette.com/How_Amps_Work.htm
    https://robrobinette.com/How_Tubes_Work.htm

    Then some of Uncle Doug's vids.



    Then
    some of D-Lab's vids. This one in particular. I would not have been able to make the jump from trying to get my head around basic theoretical concepts to actual nuts and bolts of amp workings had I not came across this. Lucky for me, it was a SF Champ. I was able to build on that knowledge when I actually made some amp repairs to the Multivox in my avatar.



    Then Valve Wizard. This is where it starts to get heady for me. So much goes over my head that I have to go back many, many times until it makes any sense. And if anything, the wiz's writing is about as basic and straightforward as one can get when you get into actual tube amp theory.

    http://www.valvewizard.co.uk/

    With these resources I have been able to repair and make functional two simple, vintage amps. Three if you count the Champ, but I'm not done with it yet.
     
    Last edited: Dec 31, 2019
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  12. trxx

    trxx Tele-Afflicted

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    I guess my biggest issue with learning anything new is the innate drive to understand things to my own level of satisfaction. And it's tiring digging for information and explanations from this source and that, where authors often repeat the same old nonsense, provide half-baked explanations, or leave giant holes where topics need to be tied together with completely missing information. For example, when I learned basics of electricity, I think most people just want to get past the fundamental theory stuff and get right into more practical concerns. I found the explanations in beginner books and textbooks on electricity and electronics very unsatisfying, as in I was almost better off not having read them. And it drives me crazy that many books and websites still to this day push the idea of conventional current, often saying something to the effect of, "Negatively charged electrons are attracted to positive, but current flows from positive to negative." That is nonsense, and it is a terrible way to teach about electricity, merely because convention. It's contradictory mud, and it sets the foundation for more muddiness further down the line when thinking about amplifying devices such as transistors and valves. And that leads into the question of how to prove charge flow direction for yourself. No book I ever found talks about that. Nor do they talk about how a person might demonstrate to himself whether an object is negatively charged or positively charged and how to prove which is which. A person has to go deep diving far and away from these books to find out anything about that and most anything else. And this is only a single type of issue in instructional books on electricity and electronics. I could write a book about bad books. I think that I'm probably far from alone in finding dissatisfaction in explanations from instructional books. But I think that I at least I have a leg up on it, in that I am often able to identify why I am dissatisfied with an explanation, rather than merely waving my hands and saying that I don't understand it. /Rant

    Anyway, that book arrived (Guitar Amplifier Electronics Basic Theory), and it seems mostly good so far. The author did blurt the typical fallacy of, electrons flow this way but current flows the other way. Grrr... But having long ago learned basic electronics theory, how valves operate, and having done some deep diving on my own for proving some things to myself, I am jumping between chapters of this book, reading the author's explanations of theory basics, reading the chapter about valves, and checking out other chapters that get into circuits. I think that overall it will be a worthwhile read, but I won't give it a thumbs up until I have read it through. I did try contacting the author before buying it to ask a couple of questions about the book, but I never got a response. I would think that in modern times with so many means for communication authors/publishers would want to hear something from their readership, but I guess that still isn't necessarily the case.
     
    Last edited: Jan 1, 2020
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  13. KT89

    KT89 Tele-Meister

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    It's not nonsense, it's the fundamental theory of how electricity works. You can't prove it yourself because it's quantum physics. Current flows from positive to negative because intuitively that's how we think about it. In classical physics, objects fall from high potential to low potential so that was applied to electronics as well; current from high potential to low potential. Because that's what voltage is: a potential. Only later did physics find out that the free fundamental particle that moves to create current is the electron, and the electron is negatively charged. As the (-) flows toward high potential, the (+) flows toward low potential. There's all sorts of discussion to be had about it, but you're right: none of it matters if you just want to fix amps. These books are written by people with degrees. People who care about knowing down to the particle level how their amps work. I get that you aren't that person, but not caring about information doesn't make it bad information. /Electrical engineer rant
     
  14. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Let's say you crack open an amp, like a Hot Rod Deluxe. Zillions of those out there, you're bound to come across one. Reverb doesn't work. Pan resistance checks out good, cables seem fine, swapping the pan doesn't help. Some quick testing shows you have signal into the reverb pan, out of the pan, but nothing on pin 7 of that 4560 op amp.

    The scenario outlined above shows one half of the op amp is working as signal goes through it into the reverb pan, but nothing is getting out of the other half of the op amp. I don't need to know *what* is happening inside the op amp, other than it's not working. Replace the part, you're good to go.

    A tube doesn't light up? I put a new tube in, it works, issue is fixed. I don't *need* a forensic investigation into why that tube failed, unless a new tube also experiences early failure in that same spot. I replaced the part, and I'm done.

    Neither of those repairs, which are incredibly common, involved any type of electronics knowledge other than reading a schematic. Honestly, I'm not good at electronics. I can get around ohm's law enough to choose a resistor wattage and guesstimate output levels, but troubleshooting and isolation will get you through 99% of stuff that hits your bench.

    This doesn't mean that information is bad, as learning just for the sake of learning is always encouraged, but I wouldn't get hung up on one point of current theory when trying to learn about how amps work. The more you look at this stuff, the more you realize every amp is pretty much the same thing - there's only so many ways you can hook up a 12ax7 and get amplification to happen.
     
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  15. Whatizitman

    Whatizitman Friend of Leo's

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    With so much information at our fingertips, there comes a point where quantity wins over quality. We can spend what little time we have trying to find the perfect resources for our perceived needs. Or we can take what we can to answer whatever current question we have as best we can to move forward. The benefit of quantity is being able to find different ways of explaining things. When one source is no longer adequate, there is plenty more out there to seek. Regardless, all the info and theory in the world means little until it’s applied. Sometimes the only way to fully understand how something works or not is by direct experience.
     
  16. trxx

    trxx Tele-Afflicted

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    Stating that current flows from positive to negative definitely is nonsense. How science usually works is that when some theory is proven to be wrong by another theory, that old theory is replaced. It's done. Earth isn't flat. And current doesn't flow from positive to negative. For reasons of 'convention' and other surrounding human stupidity (economic, political) the theory that current flows from positive to negative was kept in place. That's not science, but it still continues to be taught today in engineering. Same goes for electrons orbiting a nucleus. Science has moved on, but the influence of industry/education has not. So goes it, I guess.

    You can easily prove negative and positive charge by way of relating charges on objects. Negative and positive are only labels, and what we care about is consistency in saying what is negatively charged, what is positively charged, and the direction of charge flow. And in the same way, we can prove the direction of charge flow, using diodes and even much simpler means. And we can use diodes as another means for proving negative and positive charges. This should be foundation stuff, but for stupid reasons, it isn't in any textbooks that I have seen. The usual approach for skipping past any of this is to say that the math works out no matter which way we say that charge flows. But that is hand waving, and it doesn't clarify foundational concepts. Rather, it muddies them.

    In my mind, whether any of it matters or not depends on how well you want to understand what is going on. Showing someone picture diagrams of a capacitor and giving formulas to memorize without thinking about what is going on physically inside of a capacitor, for example, is not really teaching capacitance. By contrast, involving someone in a very simple exercise in how charge can collect on strips of foil and watching those strips move around and levitate in relation to one another very much does demonstrate concepts of charge and capacitance, and it goes about as far as is practical in proving charge polarities and other relative issues.

    Going further, modern physics shows that charge is not discrete particles, like little subatomic solar systems, but rather, is fluctuations in fields seemingly appearing and disappearing at random, like the grains of noise when an old school tv goes off the air, the sound of white noise, the noise we see in total darkness.

    Problem is, institutions of education don't want to admit what they don't know. They are the experts of education. But they are waiting for someone to tell them what to teach, according to people of power and influence. That isn't exciting. It's boring. And it's not science. This is where science is at today, and it is exciting (go to 19 minutes and 0 seconds into the video):



    Keep in mind that these theories aren't new. Faraday... Science, status, politics, economics, experts, power, influence. There is a rich history of all this stuff waiting to be discovered by anyone who wants to go deep diving.

    This should be the very beginnings of learning about charge and related issues, for kids and adults (engineers) alike:

     
    Last edited: Jan 1, 2020
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  17. trxx

    trxx Tele-Afflicted

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    What do you think? Should learning about how great guitar amplifiers work be as exciting as it is to play them? Or should it be a wading through of many broken books in hope of finding a good one and any scraps that might exist to be pieced together? Something that grandpa (and other old guys) told me is that when they were kids, radios had a sweet sound to them unlike what we have now. I don't know how true that is, but it made lots of them want to listen to them more and learn about how the things work, not to mention the quality of music back then. And lots of those old guys did learn about how those radios work.
     
  18. 24 track

    24 track Doctor of Teleocity Ad Free Member

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    I have been tinkering since I was 12 years old , its been in my blood , in high school I built 26 of the 31 final prjects ( every one kept blowing up components ) I made a police siren that played mary had a little lamb ) basically a synth , using the 9 volt power supply we built at the beginning of the class , the teacher kicked me from grade 9 to grade 11 and its been in my blood ever since.

    I have questions now but can suss out issues fairly easily, my biggest issue now is SMD I dont have the tools for the repoairs, processes seam simple enough, though
     
  19. Faceman

    Faceman Tele-Meister

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    I got into it by paying $365 dollars to have a Fender Redknob Super 210 repaired. It needed 1 tube, 2 pots and 2 resistors. I said to myself, "This is the last time I am taking my equipment anywhere to be fixed". I had always been mechanically inclined and tinkered around with electronics but that motivated me to get over my fears of the unknown. I started reading and watching Uncle Doug videos. I took on a few large amp projects then more and more work from musician friends. I still just do it as a side hobby but I love it. I get to see and work on some really fantastic gear. Just finished a 69 plexi super lead, 62 Reverberocket, and now I have an untouched never serviced 1964 Deluxe Reverb on the bench for a complete recap and service. Fun stuff!!
     
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  20. clintj

    clintj Friend of Leo's

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    Got started building pedals, then got paid to build a couple of pedals for friends. Then after playing a friend's clone tweed amp, I decided I wanted one. Built a 5E3. Built a few more amps for myself and friends, then starting getting the occasional commissioned amp. Realized that while new builds are fun, the real payback is in repairs and mods and I can bring in a little extra money to offset the cost of my tools plus build an occasional project for myself once in a while.

    Sent from my Pixel 2 using Tapatalk
     
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