Tube amps and math, say it ain't so...

[sixstringer]

Greetings all,
I received Bruce Rozenblit's latest book: Tubes & Circuit for Father's Day.
After trying (for the zillionth time) to get my head around the trigonometry and associated formulas he says are absolutely imperative if I ever hope to understand circuit design, I got to wondering if Leo Fender, Mark Sampson and other makers of great amps understood and used math at this level.
I know there are engineers here on the TAG site that know and understand electronics from a math perspective but I suspect (hope) there are others that have found ways to explore electronics and tube amp design in a less math-intensive way. So, what's the deal?, are all you guys great at math?

Rozenblit says I must have a scientific calculator.... I had one once, it's amazing how many pieces one of those turn into when launched from a 6th fl apartment window onto a parking lot.

[NickC]

Building from well documented, tried-and-true, designs is possible without a deep understanding of the math. But designing a tube amp absolutely requires understanding and ability to apply the math. There is no way around it ....... unless you have lots of parts you don't mind burning up, and patience for trial-and-error, and luck. But I'm sure most legitimate designers would argue that isn't designing at all, and I tend to agree.

0.02

[JoeCon]

Sixstringer

I recently got Merlin Blencowe's Preamp book and sure if you can do some algebra and understand OHMs' law that sure helps to understand whats going on. You can then try your values and see the results.

Even more important I think is being able to read the tube data charts and understand the graphs there. Interpolating or extending the voltages to get where you want.

You can do most of the math with a regular calculator and today there a ton of tube calculators already on line to use.

HTH....

[xtian]

I've been a member of TAG for over three years and 1500+ posts. I have built more than a dozen tube amps from scratch, often inventing my own layouts, and have learned a LOT along the way.

But I can still barely apply Ohm's Law! The stuff I DON'T KNOW about tube amps outweighs the stuff I do by 1000:1. Some of the folks here are astounding propeller heads. Many are not. But we all enjoy the process and sharing what we've learned. I think there's a place for everyone here (except the notable troll that lives under the bridge).

So fear not! Dive in head deep and paddle (carefully) around.

[vibratoking]

I believe that the math give you a complete understanding of the system you are working on. It's hard for me to imagine being highly interested in a subject, tube amps in this case, yet blatantly ignore the basic building blocks concerning that subject. I am too curious to ignore fundamental things.

I would also guess that the author of your book is introducing you to the math fundamentals that he is going use to explain the ciruits throughout his book. Without learning them, you will probably miss key points or be completely lost.

Without understanding the fundamentals, you will be limited to building by the numbers, groping for changes in the dark, and always feeling like you are working on a magic black box. If you reduce yourself to groping for changes in the dark, you will always wonder why your change worked or did not work.

Embrace the math. You don't need a math degree to get pretty damn far.

Either way there is a place for you here.

My $0.02.

[iknowjohnny]

It's like reading music and understanding theory vs someone who plays totally by ear. It not only CAN be done w/o the math, it HAS been, and by MANY ! Thing is, if you don't know it you will spend a lot longer learning things. But once you understand how values and design aspects work, you can design an amp and do it well. It just takes a lot longer because you have to spend incredible amounts of time leaning details that migth take minutes to understand via math. I can't add 1+1 but over the course of a number of years i spent tweaking several amps i learned how most every part of an amp works as far as what you can or can't do and what designs and values do to it sonically. My results took a long time because i don't know the math, but i can tell you that i now know enough to pull off whatever i want for the most part, and my amps sound and feel better than almost anything i've played. And i have access to a lot of amps including a number of hi end boutique amps.

So no, you don't need it. But i assume it will make you learn what you need to know much quicker. But no matter whether you arrive at a killer tone via ear and learning as i did, or via math and ear, either way the only thing that matters is the end result. And the fact is that a great result can be had either way. And no, i'm not talking about building by the numbers, i mean your own design. Tho lets face it, thats always going to be similar to the common designs to a large degree because it's all been done. It's the small tweaks that sum together magically that get you there, and actually those are the things least likely to benefit from math.

[tubeswell]

So, what's the deal?, are all you guys great at math?

Tube amps made me better at math

[Phil_S]

You can probably download a scientific calculator app for your phone, or you can get add-ins for Excel. Either way, it shouldn't cost you if you already have a phone or Excel. Here's an on-line one. http://web2.0calc.com/ Don't let that be a barrier

[Leo_Gnardo]

Tube amps made me better at math

Especially after getting a couple of shocks

Some of my college mates had a circuits teacher, a gentleman from the sub-continent, who would draw up a circuit on the chalkboard and point to somewhere on the drawing and ask the class in his accent "What it is here de boltage?" OK to do on the chalkboard, pencil draft etc. Don't stick your finger in the actual circuit - not recommended.

Seriously though, it is useful to know Ohms law, Power law, how to read graphs, Thevenin & Kirchoff's truths (they ain't just theories), and basic logarithm algebra so you can use & understand decibels. No point in memorizing tables of hyperbolic tangents.

[sixstringer]

Thanks everyone for your time, advice and encouragement. I've read the Merlin Blencowe books (along with many others) and got a lot out of them. I've used tube data graphs and so forth for "adjusting" circuits and so forth. I'm thankful for this age of the internet and all the apps available for electronic calculation.

I still wonder if guys like Leo Fender actually did the math while developing amps or just referred to the RCA Receiving Tube Manual (and other texts) and did a lot of experimenting.

[NickC]

.................

I still wonder if guys like Leo Fender actually did the math while developing amps or just referred to the RCA Receiving Tube Manual (and other texts) and did a lot of experimenting.

http://en.wikipedia.org/wiki/Leo_Fender

[overtone]

Understanding Ohm's law is the main key.
When I was eight or nine my grandpa connected some croc clips to me in the kitchen and flicked a switch on a red box.
After laughing like a hyena he then taught me Ohms law.
The zapping introduction is not really necessary to understand the formula, but he had a point to make about how a low voltage can still shock.

I'm not so sure that it is imperative to understand how really complicated formulas work in themselves.
To me they are tools that I plug numbers into and an output comes out the other end.
But it is just like when using a calculator - it does help to have a notion of what that "output" should be so that if it spews out kebab you don't fall for it.
I really appreciate the examples that Merlin runs through.

[bluesky636]

I received my BSEE back when tubes were still part of the curriculum. As I get closer to retirement, I decided to re-learn about tubes and tube amp designs, so I started buying a variety of books.

My current library:

If you want some books that explain all this in simple terms, these are some good ones:

http://www.amazon.com/Guitar-Amplifier- ... ap_title_0

http://www.amazon.com/How-Hot-Rod-Your- ... ap_title_0

http://www.amazon.com/The-Guitar-Amplif ... pd_sim_b_1


For more detail (and a lot of math!) I recommend these:

http://www.amazon.com/Circuit-Analysis- ... d_sim_b_39

http://www.amazon.com/Vacuum-Tube-Circu ... pd_sim_b_5

http://www.amazon.com/Vacuum-Tube-Circu ... pd_sim_b_5

http://www.amazon.com/gp/product/075063 ... 04_s00_i00

http://www.amazon.com/Valve-Amplifiers- ... ier+design

http://www.amazon.com/Tubes-Circuits-Br ... pd_sim_b_4


Just for fun:

http://www.amazon.com/Amped-Illustrated ... d_sim_b_17

http://www.amazon.com/The-Soul-Tone-Cel ... d_sim_b_14

[dorrisant]

Picking out a circuit that sounds/performs close to what you want is a good start. Or maybe just one that you are very familiar with, for example a champ circuit. Compare this to other schematics to see what makes it unique or what makes parts look like a familiar circuit. These values will give you a good baseline of values you can tweak and an idea of what you can possibly change it too.
You really need the math to make sure of component wattage or voltage ratings in your design. And to calculate gain in a stage,calculating impedances when coupling stages, determining bias values, etc.. You'll be doing yourself a favor by learning as much math and ohms law as you can tolorate.
Also, read those books you have again from time to time... There is a natural phenomenon that basically states that if you read something, even over your head, then spend some time applying what you've learned, when you reread it at a later date you will understand much more each time.

Tony

[Cliff Schecht]

The math you learn is a means to an end. I do 98% of the math I need for tube amps on a simple calculator, and it's typically just setting operating points and filter cutoffs. Very simple even if you don't know how to derive the characteristic equation for a vacuum tube or apply a Fourier transform. We aren't designing anything but single stage class A and push-pull class AB amplifiers, both have been around for 100+ years now.

Designing with tubes isn't much different than any other device, all of them have their subtleties that you should understand but the basic application is thoroughly covered in thousands of texts, videos, online lectures. This stuff really takes time and patience to soak in even for very smart people. I came into my bachelors program knowing a decent amount about analog electronics and watched some people MUCH smarter than me struggle with basic topics (especially when it came time to build stuff!). Not meant as a knock to those people either, there is a LOT to understand with electronics and each and every topic will take time and practice to really understand.

Tube amplifier design is an art within itself because we are operating these devices in their non-linear operating regions which even now isn't perfectly understood/characterized (as can be seen when one runs a simulation using a tube model). I've sunk a lot of time, money and sweat into learning tube amps and even now continue to learn more everyday. Don't expect to get everything immediately (not that you gave off that impression), be patient when approaching new topics and please please please ask questions! You have a forum full of electronics/tube gurus who are always glad to help people learn.