• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

On Line Tube Learning for newbies....

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#43
Re: Comparison of different circuit designs

pengboon said:
Anyone has a link talking about the characteristics, maybe even pros and cons of different types of circuit designs, for example, SRPP, common cathode, cascode, etc?
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Every electronic boock wil explain the basis, especialy radio-electronic books. You must be able to loan some old radio-electronics book in a public library, and photocopy it. If you are lucky, the book will be from the time where tubes was king, and in almost all cases, they will be more complet as the new books.

With tubes, you have fondamentaly 3 basic circuits: common cathode, common grid and common anode. You have exactly the same with a transistor: common emiter, common base and common collector.

After, as with transistors, you have 3 class of operation: class A, B and C. With subclass as AB1 and AB2.

At the end, and again as with transistors, you can combine 2 or more tubes to archieve circuits as SRPP, cascode, PP, ...

Now, I cannot suggest a book that will explain all. One will be good to explain the basic circuits. another will have a good explaination for the classes of operation, one will be good to explain the cascode, one will be good to explain the noise. So you have to keep reading. And experiment. Radio electronics book are best for me because they are not so academic, but practical, and as you can find every possible circuit in radio-electronics, they are talking about a lot of things.

For me, the link to radau5.ch is the best I know with free reading. But it is personnal. Other can prefer other reading. Some book on radau have the equivalent circuits of each presented circuit. Those equivalent circuits are maybe the most important part of the book, because they show how the circuits work, and which formula you must use to calculate it.

You can take a look at
http://en.wikipedia.org/wiki/Category:Electronic_amplifiers
The basic concepts are the same for tubes, the implementation is almost the same as with npn transistors, but the mathematics are not the same.
 
#47
so when people test tudes and give these ratings you have to talk to the person who tested them to find out what the numbers mean? are you sure? I was under the impression that the numerator and denominator had specific meanings
 
#48
First, I was misunderstanding the question. I thinked at those number was the type of the tube.

Now, ratings or specifications are the result of some mesurment. A specification will have no meaning at all if we don't know the conditions of the mesurment. Another issue is at we must have an unity of mesure. 120/122 doesn't tell if we are speaking of cat, money or electric current.

As exemple for the conditions, if you look at Ia=f(Ua) for a triode, the manufacturer give you the conditions. It is for which grid voltages it have mesured the curves, and we can read 1 curve for each grid voltage. For a pentode, you will have one more condition, the screnn voltage, and we will get a full set of curves for each screen voltages.

Another exemple is the music power of an amplifier. In many cases, it doesn't tell anything because the manufacturer doesn't tell anything of the conditions of the mesurment.
 
#49
oh I see, so if they just tell me a bunchof numbers it doesnt realy mean anything...the guy said no leaking and something else...I hope they are ok...ahh well atleast I only paid 11 dollars for them including shipping...thanks!
 
#50
Back to the subject of this thread.

I found a copy of Vacuum Tube Amplifiers, by George E. Valley & Henry Wallman, McGraw-Hill, 1948. It is a very technical book that deal with every aspect of tube electronics. It is not really a book for beginner because I think at most beginners don't have enough mathematical knowledge to undestand it. But, it is a very interresting reading even for someone that doesn't have a good basic mathematical background.

It is a big book, around 750 pages, and it is in 2 pdf files, a little one with the preface and the contents, and a very big one (32398K) with the book. I can do a zip and put it somewhere on the internet, but I am not sure if it is legal. The book is copywrited, but it is from 1948, so I don't know if the copyright is still valid.

Can someone confirm if I can upload this book and will not get in trouble?
 
#53
#58
Getting started with tube amps

Great ideas for reading up on tube amp basics from all of you. Thanks.....Now where do I find information on a specific amp.

I found a Bell Sound Systems PA20 amp at a garage sale. After finding the right fuse, replacing the power cord, cleaning every socket, visually inspecting each tube, and confirming all wires were attached to something, I plugged it in. Power gets to (and through) the on off switch. Nothing else seems to be affected. ...no glow, no heat, no hum. Reading another thread on this site I learned about stored power in capicitors so I have been afraid to go further.

Aside from taking it to a shop, any ideas?

Thanks! DC
 
#59
For such research, google is your friend. Otherwise, you have to follow the circuit in the amp and write it by hand. The only reference you must have for that is the pining of the tubes, and vacuum amp are not so complicated.

In your case, it can even be enough to check the filaments on the tubes with an ohmmeter and change the defect one. If it is a power tube in a push-pull, you have to change both. If all the tubes are very old, it is best to change all.

BTW, this thread is not the good thread to ask this question. It can be a lot of work to do, and it will be more appropriate in another thread. It can even be appropriate to make 2 threads, one for your problem, and another one similar to this one, but for all kind of shema we can found on the net.
 
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