Newbie needs a point in the right direction

[fleian1]

Hey everyone,

I'm fairly new to amplifier design, and even newer to this site. I'm looking to be able to design and eventually build my own amplifiers. I just had a few questions about where to start.

As far as background goes, I've researched BJT's to some extent, MOSFET's fairly little, and vacuum tubes to some extent. My tube knowledge mostly concerns static tube characteristics.

I guess I'm just wondering whether I should:

-Read (and try to understand, of course) as much theory as possible, and then design and build an amplifier

-Use the knowledge I have to analyze existing tube schematics to better understand their design or

-do whatever you guys recommend lol

Any and all help is appreciated!


Ian M.

[bob91343]

You could start with tubes. Read the RCA tube manual. The front sections have good theory information. The rear of the book has several sample designs that actually work. Also in back are tables for finding circuit values.

If you assimilate that easily you can progress to something like Terman's Radio Engineer's Handbook. Then you can acquire a piece of working gear and make some measurements to cement the theory in your mind.

This is just one way to go. If your interest is profound enough you might consider taking some courses. Lots of books out there but many of them are filled with crap. I have a friend who had trouble understanding grid leak detectors. I explained how they work and his jaw dropped - he asked why none of the books explained it in an understandable way. I said that's because the authors didn't understand it either.

[Arnulf]

Ian, have a look at this website. Since you already have experience with amplifier design you'll quickly notice similarities (load impedance and loadline are the keys, from loadline everything else is calculated). There are practical exmaples/calculations scattered throughout the text where you can quickly affirm your understanding of the subject.

If it helps in any way to somebody coming from solid-state world: JFETs and depletion mode MOSFETs are about the closest thing to tubes. If you understand how to use those, you'll figure out tubes quickly

[ray_moth]

Ian, it's difficult to know what approach would suit you best without knowing a bit about your particular strengths/interests. Some people are happy with theory and mathematical formulae; others are more practically oriented and don't enjoy too much theory.

One particular book on tubes that I find outstanding, because it covers so many relevant areas, has been designed to be readily understandable and is quite easy to read and enjoy, is Morgan Jones's Valve Amplifiers (3rd edition). The author has used sufficient math to do justice to the subject but has not overdone it, IMHO. I got it a couple of years ago by ordering online from Amazon.com. I can recommend it for most people trying to come to terms with tube amps.

[boywonder]

Here is another tube DIY educational link:

education+diy

I would also jump right in and build a simple amp to get your feet wet. You can read lots of books but it's the difference between reading about how to ride a bicycle and riding a bicycle.......

or maybe finding a dead tube amp and bringing it back to life.....

[ChrisA]

I will second two of the suggestions above. Both the "Valve Wizard" web site and the Morgan Jones Book are worth reading. They are also very much alike in their presentations and "level". The Valve Wizard is oriented to guitar amps and Jones more to HiFi but they are much the same. Both are written to the level of a person with some electronics background and high school math neither is an engineering textbook. (no differential equations) I think this is what most people want.

So to your question about theory vs. practical, these books split the difference well.

Tubes are actually very easy to build with because all the "magic" inside the tube and all so need to know is how to use them.

It would be great if you played guitar then you would have a reason to build a small single ended mono amp as you first project or do what I did and build a single tube (12ax7) overdrive distortion effects box as a first project. If you interrests are in hifi then I'd look at building a 5 watt per side amp based on single ended 6v6. Such could be built using three $40 Edcor transformers and three $10 tubes. You should know enough to design one of these just by reading that web sight before you even buy the Jones book. Later do the push pull design, but PP needs tice as many power tubes plus a phase slitter .