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Introduction/Question (Read 3429 times)
TubeNoob
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Posts: 1
Introduction/Question
01/18/08 at 08:07:12
 
As I am new to this forum, I would like to take this chance to introduce myself! I am a college student in Blacksburg, VA studying electrical engineering. I have always been obsessed with audio and vacuum tubes. Now that I am getting into some actual "electronics" classes, I am disappointed to discover that tube amplifier circuits will never be discussed in any class. I have, however, just found/ordered a few textbooks on the topic! But alas, they are not here yet. SO! the question that I have for you all: there was some talk a while back about converting the Z-plate to an Aikido audio circuit...I'm totally new to DIY tubes but am interested in this idea, and dying to get involved. Could anyone provide more information on what kinds of changes to the z-plate this would require? I would specifically like to know how this would alter the power supply circuit in the z-plate. (I don't actually know how it works anyways) It would be a great project for me to build the z-plate, listen, experiment, and then swap the Aikido circuitry, especially if the z-plate has the parts that the Aikido kit does not come with in the first place..but I'm not exactly sure what that would entail. Any information for my starving brain would be greatly appreciated! (and thanx in advance for being patient)
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Doorman
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"pouring from
the empty into the
void"

Posts: 426
Re: Introduction/Question
Reply #1 - 01/18/08 at 16:46:45
 
ToobNoob: LIke you, I'll be interested in the answers you'll no doubt get. Welcome to the forum!
                                                                                                                           Don
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Decware SE34I w/ CCE mod, ZCD, Heybrook/Linn/Clearaudio, Hagerman,
Goertz/Wireworld/cat-5/MarkAudio Alpair 10.2 drivers
(eN) in DIY Mar-Ken cabs
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Terry
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Listen with your
Heart, not with your
ears!!

Posts: 792
Re: Introduction/Question
Reply #2 - 02/11/08 at 08:26:27
 
Toobnoob,

Welcome to the forum.

I would suggest you get your basic tube circuit design foundation first.  All other circuits are basically derived from the basic grounded cathode topology.  This basic circuit will help you become intimately familiar with the NEEDS of any tube your working with.  Here is a thread in which I propose a basic way of calculating tube voltage requirements for a grounded cathode topology.  This is basically what the Zen Plate uses as a topology.  Then I would further suggest that you get familiar with the cathode follower and how it works.  Once you understand those two circuits many other circuits start to make a LOT of sense.

The one thing I borrow from the Akido circuit is ripple cancelation, but I use a white CF to accomplish this.  To be honest I don't really understand why certain things are the way they are in the Akido circuit, what I have done makes a lot more sense to me and WORKS, so I am not worried about the Akido circuit and how it works really.

Here is a thread I started to help a few new to tube gents get their feet wet on tube circuits.  If you know ohms law this should make things a LOT easier.

http://www.hawthorneaudio.com/forums/viewtopic.php?f=8&t=1784

I basically find a Plate Characteristics chart for a tube I want to design with (enlarging it as much as I can on my screen), and then push my "print screen" button on my keyboard.  Then I paste it in MS paint, and further cut and paste just the chart in a file all its own, and save it.  I can go back and work out various load lines and how they will perform for me BEFORE actually breadboarding a circuit.  This has saved me a LOT of time in working out the bugs of circuits.  I was struggling with this for a while but kind of figured this methode out on my own, and it works real well.  I imagine that others do something similar, or they may just do all the math without worrying about the load lines and how that all works.

One thing you will notice as you work with load lines, is that the higher the voltage of your B+ the more horizontal your load line will be, also allowing greater voltage swings with your tubes AC output, making it easier to drive many different power tubes.  Often you won't need as much AC voltage swing as you will have designed a circuit to accomplish, but it can't hurt anything.

I hope this helps, any more Q's can be directed here or you can PM or email me for further questions.  At the Audiotalk forum Eli Duttman is starting a DIY project of a single ended pentode circuit, you might want to follow that to see how it develops, it might help you gain more understanding as well.

TG


P.S. If you like me you will be disappionted with the education end of your venture into electronics.  They teach you theory that may or may not be what you need to know later, and you will no doubt learn more from your work later after your education that will give you what you need to really know.  I have learned more from other indiviuals on how to trouble shoot and design circuits than I ever did from school, but school gives you all the tools.
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« Last Edit: 02/11/08 at 08:30:24 by Terry »  
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Crazy Bill the Eel Killer
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Tubes Rule !!

Posts: 85
Re: Introduction/Question
Reply #3 - 02/11/08 at 13:43:07
 
Hello Toobnoob,

Like you I was a complete newbie a few years back when I started, and I have found this forum, EV's forum(the link Terry provided you with), and the internet in general to be an unlimited supply of usefull knowledge.

Terry's advice to study the grounded cathode and cathode follower topologies is sound advice. Use the internet, just enter those items into your search engine and be prepared to study. Make sure you buy lots of printer paper as there is a ton of info to download.

Here's a great link to get started.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=38278

After you do some reading, you can ask specific questions on either of the forums. Everyone is very helpful.

Terry's advice about Ohm's Law is dead on. Learn it, and also learn Kirschoff's Laws on voltage and current. Once you understand those, the rest will fall into place.

Take it from me ( I know from experience ), there is no such thing as a stupid question. Feel free to ask anything ( I did ).
You will find both these forums to be full of friendly people willing to help. ( and the fact that there are a few bona-fide genuises who actually know what they're talking about on them doesn't hurt either ).

Welcome to the forum and to a great hobby.

Cheers,                  Crazy Bill               Smiley
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Terry
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Listen with your
Heart, not with your
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Posts: 792
Re: Introduction/Question
Reply #4 - 02/11/08 at 17:43:31
 
Bill,


Wow! I have never seen many of those links, but I have books and have seen some of those that I still consider the best online tutorials like the NEETS site.  My point and why I made that post on the HT forum was that I read for years theory for the longest time and none of them told you how to design a circuit.  My post by using the simpliest methode I could think up was to use ohms law with the most basic methode.  

What you will learn is if you make a circuit and listen to it, is why one circuit sounds better (or different) than another if you have the load lines for each.  You will also become familiar with the effects of 2nd order harmonic distortion, especially when at lower wattages you have little distortion, but because at the load line extremes you have less linearity you will have more.  So aspects of the music like bass, that take more power will distort more, sometimes imparting some desirable effects at first.  For instance a preamp that is designed this way will seem to add bass to the signal, because distortion in the bass region often sounds like more bass, when in reality it is the same but not as clean (or tight as some would say).  Just doing some basic measurements will reveal what is happening in a circuit.

In the end you can read all day long but nothing will help more than taking one tube and making an amp with it and trying many different operating point schemes.  You will end up with a basic sound of the tube,  but you will find you can change it to sound very different at various operating points and load lines.  Don't always think that distortion is bad though, it can be a nice feature when used judiciously, of an amplifier where and how much is what you can control.

TG
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