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Hoffman Amps Forum image Author Topic: Recommended books for learning amp electronics?  (Read 6329 times)

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Offline newguitarsmell

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Recommended books for learning amp electronics?
« on: December 20, 2018, 12:41:26 pm »
Thanks for all the help, guys. I am feeling like I need to better understand how all these electronics go together. I have read Rob Robinette's site cover to cover. Anybody have any other recommendations for good basics?


Also - I have an amp with a SS rectifier. How do I determine what tube I could use to replace it?

Offline sluckey

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Re: Recommended books for learning amp electronics?
« Reply #1 on: December 20, 2018, 02:18:29 pm »
Look at this...

     http://el34world.com/Forum/index.php?topic=3273.0

What kind of amp? Got a schematic?
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline jjasilli

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Re: Recommended books for learning amp electronics?
« Reply #2 on: December 20, 2018, 07:45:14 pm »
Dave Funks Tube Amp Workbook
Inside Tube Amps, Dan Torres
Tube Amp Book, Aspen Pittman
Jack Darr, Guitar Amp book free pdf online
 

Offline plumcrazyfx

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Re: Recommended books for learning amp electronics?
« Reply #3 on: December 31, 2018, 07:51:14 am »
If you are really wanting to start from the beginning, I started with a set of correspondence school electronics books from the 60s that I got from a garage sale.  Good because they we teaching both tube and transistor at the time. Can probably find them online.

Offline 1blueheron

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Re: Recommended books for learning amp electronics?
« Reply #4 on: January 01, 2019, 03:27:56 pm »
Newguitarsmell,

I am right there in the trenches with you trying to learn.  I have trouble translating some of the terms, abbreviations, and jargon used by more experienced and learned tubers into plain English I can understand and use.  What is a grid dropper?  What is a condenser input filter vs. a choke input filter? What does HT mean and what is the difference between point "B", "B+" and "B-"  what is the difference between earth ground,  star ground, single point ground, chassis ground, floating ground, and electrical ground?  So many term are used interchangeably or the same things drawn differently by different people and called something slightly different.  Why do some people call amps single ended while others say class A or whats the difference between push pull vs class AB.  After 6 months, I feell= like I am just now starting to be able to understand some of this strange foreign language but I certainly don't speak it fluently.  Maybe enough to buy a cup of coffee or ask directions...

I work best from pictures and illustrations.  So far I have found this article to be one of the most useful as it has a great set of illustrations with it that are well labelled.

https://www.premierguitar.com/articles/17116-how-tube-amps-work?page=4

On the advice of Sluckey and a few others, I got an amp that is fairly basic, just to rebuild/modify/learn before I start building amps from scratch which is my goal.   I paid 100.00 for the Airline 8504 which is about the same as a used Epiphone Les Paul Jr.  used to sell for if you can find one now. My first goal is to make sure it is up and running in fairly stock form.  Then maybe do some mild mods to see how it changes the sound etc.

My first project was to get a schematic, redraw that schematic line by line (this helps me fix what is tied to what in my mind), identify each section of the amp (power section, preamp section, tremolo section, phase inverter, output section.  Identify every component represented in the schematic and how it functions in the circuit.  Filter capacitors vs. coupling capacitors, vs bypass capacitors vs. tone capacitors etc. and the same for resistors.  Learn the different material compositions of resistors and what effect they have on sound and where they are best used.

To do this, I went through the amp and put little stickers on all of the capacitors with their number designation on the schematic.  This was fun in its own way and now I have a picture reference rather than just a schematic on paper.  Next I plotted all of the resistors with their color code on the schematic.  That lets me clearly identify where each one is in the amp and what/how it connects to.  Since a lot of schematics don't show the grounding path but rather just use a ground symbol, it can make tracing things for a newbie challenging.  All of the wires are not always shown on the schematic.

I have spent a lot of time tearing old equipment apart.  Salvaging each part and in the process identifying what it is, what it was used for, what it can be used for and filing it away.  This has helped me learn a great deal.  For instance, a couple days ago I was salvaging resistors.  Orange drops, brown drops, green drops, blue drops, etc.  then I started sorting them all by value.   .056uf, .082uf, .15uf etc.  then came a green drop with marked .001K   :w2:  Gotta figure that one out... do resistors come packaged in green drops...

The small capacitors that look like resistors with painted on stripes always seem to fool me.

It's hard to find some of this stuff on web sites or in books and FAQ's.  Some I think just comes from experience and making mistakes and learning from them.

I will say the folks on this site have been very helpful and kind to me as a newbie asking stupid questions.  Of all the references out there, it amazes me how many times Google ends up pointing me back to el34world and how much info is contained in the schematic library etc.

My wife bought me a book on building tube amps for beginners.  Will get the name of the author tonite if I can remember. and post here.


Offline Ritchie200

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Re: Recommended books for learning amp electronics?
« Reply #5 on: January 01, 2019, 11:37:22 pm »
1blueheron, thanks for sharing your journey!  Interesting what you said about your google searches bringing you back to this forum.  Doug has spent years putting fantastic information on this site, all you have to do is poke around a bit.  In my humble opinion, better than a lot of books out there, especially if you are just starting out.  Also, just keep up and read the posts - even if they may not apply or reference your particular amp brand interest.  Many times its the little nugget of information from the least likely place that brings it all together.  I always say I learn something new here every day.  There are some fantastic folks here who freely give of their time and knowledge.  I am always in awe of their generosity.


Jim

My religion? I'm a Cathode Follower!
Can we have everything louder than everything else?

Offline Twosteps

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Re: Recommended books for learning amp electronics?
« Reply #6 on: January 02, 2019, 12:47:11 am »
Just realized I have Jack Darr's book to somewhere, never finished it yet neither have been using it as a reference since I've forgotten that I have it. A lot of my google search brought me to this forum which I ended up registered and shamelessly asking a lot of questions. I am now at my 6 build and just about to understand it a lot more now. Couldn't thanks people in this forum enough with their helpful answers.

Offline 1blueheron

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Re: Recommended books for learning amp electronics?
« Reply #7 on: January 02, 2019, 04:57:12 am »
The name of the book the wife got me is Vacuum Tube Amplifier Basics  by EJ Jurich.  Not specifically focused on guitar amplifiers but more on basic building blocks of tube amps.  Knowledge generally transfers to guitar amps...

Offline d95err

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Re: Recommended books for learning amp electronics?
« Reply #8 on: January 02, 2019, 06:03:40 am »
Also - I have an amp with a SS rectifier. How do I determine what tube I could use to replace it?

Simple answer: you can’t.

A rectifier tube requires a separate heater winding on the transformer, which won’t be there if the amp is designed for SS rectification.

If you want to emulate the effect of a tube rectifier, you can insert a power resistor of something like 100 to 300 ohms between the rectifier and the first filter capacitor. It needs to be a 10W or more resistor, depending on the amp.

Offline jjasilli

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Re: Recommended books for learning amp electronics?
« Reply #9 on: January 02, 2019, 01:18:10 pm »
The name of the book the wife got me is Vacuum Tube Amplifier Basics  by EJ Jurich.  Not specifically focused on guitar amplifiers but more on basic building blocks of tube amps.  Knowledge generally transfers to guitar amps...


The books I posted in Reply #2 are specifically for guitar amps; they're an easy read and helped me as a beginner.  There are more complex guitar amp books for later on.


Also, Doug just posted to the Rob Robinette site which pulls together a host of useful & informative Fender amp mods:  http://el34world.com/Forum/index.php?topic=24122.msg259156#msg259156

Offline Davidg

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Re: Recommended books for learning amp electronics?
« Reply #10 on: January 02, 2019, 02:33:44 pm »
I have most of the beginner books on tube and guitar amps and for me the most "bang for your buck" type book I found was " Design and Construction if Tube Guitar Amplifers" by Robert Megantz. It is not one of the more popular ones and I have never understood why. I actually got it too late I suppose because I didn't find anything new in it but I ihave to say if I sold off everything and could only keep one book that would be it and I have a pretty good library of tube amp books including the hard to find jack darr book (great book on repair and ttroubleshooting) and all of Merlin's excellent design-oriented books and Gerald Weber's and TUT volumes and so on and so on...... Megantz's book is by far the most concise with all info you need to design and build any type of tube guitar amp you wish including chassis construction and layout and design and tone shaping tweaks. Good Luck!

Offline DummyLoad

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Re: Recommended books for learning amp electronics?
« Reply #11 on: January 02, 2019, 06:35:01 pm »
Also - I have an amp with a SS rectifier. How do I determine what tube I could use to replace it?

Simple answer: you can’t.

A rectifier tube requires a separate heater winding on the transformer, which won’t be there if the amp is designed for SS rectification.

If you want to emulate the effect of a tube rectifier, you can insert a power resistor of something like 100 to 300 ohms between the rectifier and the first filter capacitor. It needs to be a 10W or more resistor, depending on the amp.


depends. on the amp - it may possible to add 6CA7 to a low(er) wattage amp with 6.3V fil. string.


--pete

Offline jjasilli

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Re: Recommended books for learning amp electronics?
« Reply #12 on: January 02, 2019, 07:30:37 pm »
Yes.  You could also add a tranny to supply the rectifier tube filament.  But there's an easier way - simulation - add a power resistor to drop the B+ voltage.  I use an inductive power resistor to further simulate the reactance of a tube rectifier.


To spec out a tube rectifier, go to the tube charts to see how much plate + screen current is drawn by the power tubes at the B+ voltage in your amp, and at their bias point.  (Or, you could measure it.)  Pick a rectifier tube that can handle that voltage & current draw, per the tube charts.  You can look at the schematic of similar amps as a guide. 


Note that ea type of rectifier tube has an associated "voltage drop".  A drop from where?  From the 1.414 factor for SS rectification.  If you keep SS rectification, once you know the current draw you can use Ohm's Law to determine the value of a power resistor to match the voltage drop of various tube rectifiers.  Somewhere on this Forum should be a chart of many rectifier tubes and their properties.

 


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