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74Elsinore 20th October 2004 07:03 PM

Help an ME learn the basics?
 
Guys I did a search and found some of the information I am looking for, but not all, soooo...

I want to get started on some projects but I need to know some background. I am an engineer by profession BUT I am an ME. I am interested in all things audio: guitar amps, audio equipment, etc. I have read a lot of the great write-ups on this site and others and I get lost pretty quick.

As an ME, I had the basic junior-level electrical circuits course, what they called "Circuit Analysis", i.e. basic circuit theory. We did all the basic stuff like voltage dividers, series and parallel circuits, Thevenin equivalents, phasors, basic power calculations, RLC circuits, blah blah blah. And that's where it ended.

So when I hear you guys talk about tube circuits and transformers and electrolytic caps, I get all excited but shoot I don't know where to start.

Example: I know what impedance is (at least I can calculate it from Z=Ijwt), but why do I need a transformer to match impedances? Why do they need to be matched at all?

I wouldn't know a transformer if it slapped me upside the head. I have no idea what an op-amp is. Does a vacuum tube do the same thing as a transistor? How do I tell if a cap is any good? Where are the taps for a transformer? Stuff like that.

So my question to you fellers is: how do I get started? Where do I pick up from where I'm currently at? I THINK I know what a capacitor looks like and I THINK I know that what you call a choke is actually an inductor, but...

I do know how to use most of the features of a VOM, just from using it on my car. I never hear any talk of phasors or imaginary numbers on the site so I think there must be a shortcut way around that. I saved my circuits book so I can go through that and do a quick review.

So - I definitely have the right technical background but I am missing some other knowledge, perhaps more technician-based rather than engineering-based?

I would love to do a tube or SS project but I don't know where to start. I could cook-book it by just following the schematic, buying the parts and soldering it together but I couldn't troubleshoot it if something was amiss, plus I think I need some basic instruction in safety when working with those voltages. The circuits class I had did not have a lab segment. Unless you were an EE you didn't get the lab section. No fun!

Thanks guys!

Cal Weldon 21st October 2004 10:06 PM

Re: Help an ME learn the basics?
 
Quote:

Originally posted by 74Elsinore
how do I get started? Where do I pick up from where I'm currently at?
I think if you have a specific project in mind, you might get a better response. It seems that you have the desire, how 'bout giving us an idea what it is you want to build and maybe you can be steered in the right direction.

Cal

sek 21st October 2004 11:30 PM

Yep, such things always get explained much quicker with examples. ;)

Let me respond to your particular concerns, just to get you started... ;)

Quote:

I wouldn't know a transformer if it slapped me upside the head.
I doubt that ;) because transformers are among the heaviest electrical components we deal with (besides enclosures and speaker chassis). ;)

A transformer basically is a 'set of inductors' which are coupled together electromagnetically (via sharing the same core). The most common example in the world of transformers as technical devices are shurely power supply transformers. You find them in almost all electrical devices that have mains power connection.

But you are right, they come in so many kinds that there definitely are transformer which can't be easily recognized as such (though those are most likely the smaller ones that don't hurt when slapping you upside the head). ;)

All you need to get started on transformers and their uses would be some basic literature about electricity/electronics. Once you've selected a particular project to start with - and should this one contain a transformer - just ask back, as it makes no sense for you to study every possible transformer use case in the first place.

Quote:

I have no idea what an op-amp is.
As this is a slightly more complex topic, I stop kidding for a moment and recommend literature from the source, to start with. Many opamp-manufacturers supply very good (or at least very much) online literature (PDFs) as Application Notes, Journals and Documentations. I can't recommend anything specific, but in general, companies like Analog Devices or Texas Instruments have plenty of resources. Regarding paperwork, Walter G. Jung (Walt), a renowned Analog Devices author, can surely be recommended.

Someone more experienced would now have to prevent me from recommending the Active Filter Cookbook by posting better alternatives! ;)

Quote:

Does a vacuum tube do the same thing as a transistor?
Just tell that to a Tube Dude! He'll instantly throw a transformer at you! ;)

Did I mention that a frequent use of transformers in DIY audio is impedance conversion in tube circuits? ;) ;) ;)

Well, tubes are a complex topic on their own, something you would have to look up in dedicated books/literature, as most electronics textbooks don't cover them (any more).

Regarding transistors, their principles are covered in electronics literature, but for a better understanding I strongly recommend dedicated transistor books. I can't help you with recommendations for those, as you probably don't want to start your survey with looking up east german prints from the seventies, let alone reading them... ;)

Quote:

How do I tell if a cap is any good?
Well, this is a topic where taste plays a role that I assume overrated (I only answer this question to tell you this fact).

Capacitors differ by construction type and used materials. They have different electrical and mechanical properties and different types are useful for different purposes. The appropriate way is to find out which capacitor type (polarized, non-polarized) best suits (or is required for) the particular use in a particular circuit, then find out which material/make and properties work better than others, never forgetting the required electrical and mechanical properties (upper and lower limits and availabilites) and cost. Only then comes a decision regarding preferred taste or maybe magic characteristics.

Capacitors are also very basic components from a textbook view, they should be explained in the book you aquire to learn about transformers, transistors and everything else. ;)

Oh, and as of their construction, they should be very easy to understand for an ME :D

Quote:

So my question to you fellers is: how do I get started?
Well, you're actually asking a lot of question for a 'beginner'. I really consider this a good thing, try to get the big picture as long as you can! But it's too much to cover it all equally quick in equal depth.

As Cal pointed out, just throw in a particular project that you might have in mind. Even if you don't really want to buld it - but learn how understanding it is best approached - it makes talking about components and standards a lot easier.

You see, there is no dedicated compendium or tutorial to enter the DIY audio world that I know of, but maybe this is a lack of capability of DIYAUDIO as of yet. Nobody seems to ever have questioned the availability of those informations the way you did. Perhaps Diyaudio.com could make use of some compiled starting point for the EE and components aspects view; despite the many 'sticky' threads in the subforums with plenty of collected (but spread and uncompiled) material.

Quote:

I never hear any talk of phasors or imaginary numbers on the site so I think there must be a shortcut way around that.
Well don't ask me about phasors, but shortcutting a way around higher math is something I consider an actual lack of many diy audio protagonists. Don't try to get rid of the theoretical background! :cool:

Even so, follow that interest in safety! Always make shure that safety comes first, as you are likely to work with mains transformers... :D :D :D and other dangerous things.

Sebastian.

JoeBob 22nd October 2004 12:52 AM

Best source of info for a beginner would be Rod Elliott's site ( http://www.sound.westhost.com ). Shoot down there, and then click on articles, there will be a section called "Beginners' Luck - The beginners' Guide to ..." and he's got articles about electronics basics as well as the basics on transformers, since you brought them up, if you read through that you should be understanding more of what goes along here. But mind you, the best way to learn is through experience. Pick up a spice modeling program, look at the examples, change things, see what happens, try to understand why, etc etc etc...

As for the math, we'll, alot of what goes on here doesn't involve people measuring often, alot of people are more conserned about the way something sounds to them, which isn't bad, but it's refreshing to read some posts that explain the physics behind some concepts by the more learned of the members here.

Brett 22nd October 2004 03:17 AM

For tubes, the best primer I could suggest is John Broskie's Grounded Cathode Amplifiers which is very well explained and easy to follow. It describes the most basic and commonly used tube amp topology. There are also a ton of other well written and thought out articles there should that one pique your curiousity.

There is also a US Navy electronics training package available online somewhere, that covers a lot of other stuff like solid state, but I can't find the URL. Someone else will know it though. Others will also likely chime in with recomended texts available in the US that you could pick up cheap.

I agree with the other posters that it's best for you to choose a project and start with that, then you can ask specific questions and answers and see how they relate to something you're doing. I've always found it best to try a project that you'll actually want to use too, rather than something that's a thought exercise, ie don't build a 2W amp when you need 100W.

Brett 22nd October 2004 03:54 AM

This thread should also supply you with a heap of reading, incl the Navy series I mentioned before.

http://www.diyaudio.com/forums/showt...794#post496794

Have fun.

cunningham 25th October 2004 11:29 PM

The best explaination I know of for an ME ...of what a transformer does is to compare with speed vs torque. If voltage is speed, and current is torque; The transformer is like the transmission in a car. A lower impeadence is like a lower gear, lots of torque(current) and little speed(voltage). A higher impeadence is like high gear. The power from the engine comes with only one speed range and one torque range. The transmission has to transform the energy to match the right mechanical impeadences.

All the power is transformed into a different voltage vs current, but it is still the same amount of power. Of course in the real world, the transmission in a car has losses. Mainly friction. There is friction inside a transformer to. Core losses created by iron atoms moving around into each other and also there is some copper losses in the windings. This is why a transformer will get warm even with no load connected. No system is perfect, electrical or mechanical. :rolleyes:

TaaJ 26th October 2004 10:40 PM

Quote:

Originally posted by Brett

There is also a US Navy electronics training package available online somewhere, that covers a lot of other stuff like solid state, but I can't find the URL. Someone else will know it though. Others will also likely chime in with recomended texts available in the US that you could pick up cheap.
http://www.tpub.com/neets/index.htm

This one?

If so, very good reading. I'm still reading it, as I'm also learning.

74Elsinore 27th October 2004 10:54 PM

Guys thanks for the terrific replies and all the great links.

The transmission allegory to impedance is a good one, although I am primarily a fluid flow guy. I am familiar with the current-flowrate and voltage-pressure metaphors. I also remember that the 2nd order DE for a series RLC curcuit has the same form as the one for a spring-mass-damper system. And a lot of the e^jwt stuff shows up on both sides too.

So - it sounds like I need to find an easy project to get started with.

Thanks ! ! ! Pete

RHosch 28th October 2004 02:14 AM

Yes, there is an analog for each component in electrical, fluid, and mechanical systems.

If I remember correctly (hell, I'm sure I don't, but I'll give it a shot):

Code:

Mechanical        Electrical        Fluid

Damper                Resistance        Resistance
Spring                Inductor        Inertance
Mass                Capacitor        Reservoir
Force                Voltage                Pressure
Velocity        Current                Flowrate

OK, I'm not so sure about that last one. Also, there is a difference in, I believe, the equation form of Resistance between electrical and fluid systems. I believe what is "R" in one form of the equations becomes "1/R" after a transducer. Been a while since I actually thought about that stuff.


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