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My impressions of learning electronics

  1. Dec 21, 2016 #1
    A second look at a first impression of electronics.

    When I decide to take up electronics repair of vacuum tube amplifiers as a hobby I had little idea of what I would need to learn. There were many ups and downs in the process. None the less, within a relative short period of time I found I was able to repair amps. Some were pretty easy and others were a bit perplexing.

    I got a lot of help here on the Physics Forum,so thanks to everyone.

    I assumed that these devices were not too very complex. Although the circuits are not difficult to understand, this old technology is anything but simple. Detailed Information concerning the various components such as transformers for example is not easy to find if it can be found at all. Various arcane codes on capacitors still give me problems. In any event, the repair work got done correctly.


    I next got the “bright idea” that I could build reproductions of old amps. That actually went pretty well for low wattage amps without effects such as reverb. When I decided to try to build more complex higher wattage amp things did not go so well.

    The main issue in the higher wattage amps was the problems of hum and hiss. This was due to my lack of experience and understanding of the realities of proper lay out and of powers supplies. Hum and hiss in guitar amps is a common problem that even the well-known commercial manufactures often don’t get right.


    Building amps on turret boards is not common in today’s world except for a few “reissue” amps from the major manufactures. Turret board construction appears to be done mostly by hobbyist and a few small boutique commercial builders. I have yet to find much information on the best ways to lay out turret boards and examples of well thought out grounding schemes.


    It also appears that design software commonly used to assist in designing digital electronics is not well suited to the development of vacuum tube amps. There appears to be a large amount misinformation being kicked around on the internet. Sorting out fact from fiction has been a perplexing issue for me. Of course, this is just my limited understanding of the subject and very well may be in error.


    This whole adventure has been both entertaining and frustrating at the same time. I have taken on several other hard to do things in the past, such as becoming a commercial pilot. I never had one moment in those endeavors where I thought I could not learn to do it. Well...in my youth I was bulletproof like most young guys are...lol
    I am not so sure about this electronics hobby!


    Cheers,


    Billy
     
  2. jcsd
  3. Dec 22, 2016 #2

    Nidum

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    Do you have access to magazines like Practical Wireless from the 1930's to 1960's period ? These were full of really good circuit designs , basic theory and information about what the professional builders were doing .
     
  4. Dec 22, 2016 #3
    Hi @Planobilly - I'm interested in much the same things are you & got here roughly the same way. In my case, I was interested in both electronics & physics as a kid in high school; however being not so good at math, I didn't pursue either subject in college. Roughly 30 years later, I now find myself interested in both topics again; and my point of entry was having troubleshot & fixed noise problems last year in a tube guitar amp. Since then I've "designed" (load lines, etc.) and built a few simple DIY guitar preamps & a simple single-ended power amp. I may or may not do more designing/building, but either way I'm interested in picking up physics/electronics again and this time around doing more with the math.

    Morgan Jones has a very detailed (obsessive, actually) book on tube amp layout. His niche is hi fidelity, not guitar, but that is not a big deal; however, he favors PCB over turret, so you might not find it as useful as you'd like. Even so, he has good tips in other areas, e.g. chassis fabrication, cooling, etc. https://www.amazon.com/Building-Val...8&qid=1482406421&sr=1-3&keywords=morgan+jones, 2nd ed.

    Perhaps more accessible are the two books by Merlin Blencowe; like Jones he is based in the U.K.: Designing https://www.amazon.com/Designing-Tu...id=1482406478&sr=1-3&keywords=Merlin+Blencowe, 2nd ed., and https://www.amazon.com/Designing-Hi...id=1482406478&sr=1-1&keywords=Merlin+Blencowe. He also has many helpful articles on his web site - http://www.valvewizard.co.uk - including a PDF of his excellent chapter on audio grounding, taken from the guitar preamp book. Many helpful layout principles for minimizing noise. Of the two books, the hi-fi book is his latest & by far the most comprehensive; it begins with an excellent electronics primer, which is very much physics/EE-based, and the back of the book features a section on power supplies that is very helpful. The guitar amp book is still helpful as it covers inputs & tone stacks that you won't find in the hi fi book.

    If you just want software to draw schematics, the Eagle PCB editor has a free version that is more than adequate; if you Google you will find libraries that various users have contributed with all the vacuum tube symbols you need, plus symbols for input jacks, etc. If you want to simulate vacuum tube circuits, you can use LTSpice, which again is free; and again if you Google you will find that users have contributed libraries w/ vacuum tube models & symbols. Layout software is also available, although so far I have just used general purpose drawing tools, e.g. OmniGraffle.

    Lastly, in addition to any electronics help you might get here on this forum, there are a couple of decent guitar amp forums you could check out - although maybe you already have? These are: 1) The Gear Page's Amps/Cabs Tech Corner - there's more chaff than wheat, but but there are a handful of EE's who know a great deal & tend to be quite helpful once you get their attention; and 2) Music-Electronics-Forum.com, which again has quite a few EE's plus quite a few boutique amp builders who are very knowledgeable.
     
    Last edited by a moderator: May 8, 2017
  5. Dec 22, 2016 #4

    jim hardy

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  6. Dec 22, 2016 #5
    Nidum...thanks, I will check out the books.

    Usable Thought, thanks a lot for all the information. I have read a lot on the valve wizard site. His descriptions are clear and easy to read. I will be sure to check out all the other links and information you posted. Again thanks!

    Mr. Jim, It looks like some interesting equipment. I have no idea what the reserve is but I am going to bid $100 just in case...lol Now Jim, if I win the bid you will be required to come visit your kids and help me set it up...lol Also we will go fishing if you like. You are always welcome here in Homestead!!!

    Cheers,

    Billy
     
  7. Dec 22, 2016 #6

    jim hardy

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    That'd be a pleasure. Your house is about a half mile from my kids' house. Would sure be fun to hook up with Anorlunda in Marathon...
     
  8. Dec 22, 2016 #7
    The boat is in Marathon Jim, tugging at the dock lines...lol
     
  9. Dec 22, 2016 #8

    dlgoff

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    I was lucky when I first got into tube type radios, etc as a kid; which was pre-transistors time. I would find all sorts of discarded radios at a junk yard, bring them home, then get them working. I was able to build up a stock of vacuum tubes and other components. No books, no teacher. Just trial and error. Later I learned a lot from my old ham mentor. After that, transistors; much better.

    BTW I fish. :oldbiggrin:
     
  10. Dec 22, 2016 #9
    Well Don....the fish are biting down here as we speak...lol
    You should come visit me!! I don't need much of an excuse to go fishing!!

    The "good old days" of discarded tube electronics is long gone. What use to be junk is now high dollar antiques!!

    Cheers,

    Billy
     
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