Starting Point for Amp Info/Repair?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by gtrfinder, Mar 10, 2008.

  1. gtrfinder

    gtrfinder Supporting Member

    Oct 10, 2006

    First of all I'm not an engineer, electrician, amp builder, modifier, or anything of the sort.
    Basically all I'm able to do is change the tubes in my amp. I cannot bias a fixed-bias amp, or even solder for that matter.

    I'd like some recommendations on some reading material (via books, the internet, or whatever else is useful) to gain some basic knowledge of electricity and how an amplifier works. Partially for the knowledge aspect (I'm very interested in it), but also because I'd like to be able to bias, and solder, and just have a working knowledge of these sorts of things.

    Any info would be greatly appreciated.

    DISCLAIMER: I realize that there is a great potential for harm when dealing with electricity. It seems that every time a thread is started on biasing here on TGP someone mentions how dangerous it is and that they should probably take it to a tech.
    While I will not discourage you from warning me about the dangers of electrical circuits, I will ask you:
    Please take into account that 1) I have read and are aware of many of these warnings, 2) I do not intend to do anything other than gain some basic knowledge and skills, 3) Take full responsibility for what I choose to do
  2. AL30

    AL30 Member

    Jul 20, 2005
    The Guitar Amp Handbook: Understanding Tube Amplifiers and Getting Great Sounds by Dave Hunter is a great jumping on point for some basic understanding of tube amps. Again this is a good overview - as you progress you'll want and need more knowledge but for now this should be a good fit.

    This book does not teach electronics or electricity. If you want that you'll need to look elsewhere.

    Hoffman Amps also has some helpful info on line - scroll down.

  3. epluribus

    epluribus Member

    Dec 14, 2005
    Both Jack Darr's book and good old US Navy NEETS are available, legally, online. Darr is a quicker read, NEETS is a full-blown independent study course. I'd also recommend perusing, Randall Aiken, and Tone Lizard for a quick start.

    But to really bring the theory home, nothing beats hands-on. A bud (an automotive audio engineer) showed me how to safely pull a chassis, drain caps, etc. Having done that (which was really very quick) I nabbed a pair of Kalamazoo Model IIs on EBay, one in near-showroom condition, and one orphan for twisted experiments. The OEM one establishes baseline performance for the original circuit--and looks cool. The orphan even now is jumpered to a breadboard so that I can run out to the shop and stick a circuit together or try out a mod when I read about it. (People keep asking me when I'm going to "finish" the amp. Hmp. Never? :))

  4. Blue Strat

    Blue Strat Member

    Aug 2, 2002
    Sterling, VA (not far from Washington DC)
    A good hands on thing to do next is get a bias probe and start using it. You'll need one for repairs or just installing new power tubes. These are also an excellent tool for diagnosing or assessing the general health of an amp. They can give you a lot of indications without even pulling the chassis....very much like using a stethoscope on a person.
  5. pgissi

    pgissi Member

    Nov 23, 2006
    Outta Here
    In this order-

    Getting Started in Electronics by Forrest Mimms III (radio shack)EXCELLENT Electronics 101 instruction and a fun read, not long
    Guitar Electronics by Donald Brosnac
    Electronic Projects for Musicians by Craig Anderton
    Understanding Power Supplies (radio shack)
    Tube Amp Book (Aspen Pittman) good ground floor tube amp book

    Once you have those in you, graduate to (AND DONT KILL YOURSELF IN THE PROCESS)-
    Desktop Reference of Hip Vintage Guitar Amps (Gerald Weber)
    Tube Amp Talk (Gerald Weber)
    Tube Guitar Amplifier Essentials (Gerald Weber)

    There is some overalap with his books here but I own the Desktop and Talk book and they have a different focus generally. There are also other books, I just forget the titles and authors but Gerald does a fine job of schooling you as long as you are ready for the info

    Great Books

    But on the subject of Bias, the info is more elusive, its out there but its rarely a complete and thorough explanation.

    For one piece of the puzzle, you can thank this guy, you will understand once you get the info from the books above in you, you have a lot or reading to do-

    See "how to Biasing" Videos and once again Please dont kill yourself there are several hundred DC volts on a tube and it will kill you
  6. epluribus

    epluribus Member

    Dec 14, 2005
    Hey Mike.

    What other sorts of info can you get from a bias probe? I learned to set bias with a DMM and have done it that way ever since--hence no probe. Though I get lots of mileage out of measuring all sorts of things in my cicruits with the meter, you've piqued my curiosity.


    ps...In all the mention of good web sources for tech info, don't forget a little outfit called KCANOSTubes. The guy in charge is 'sposed ta be an OK joe. :AOK

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