My first scratch-built Vacuum Tube Amplifier: "Big Red"

[N2IXK]

Great to see another tube geek here!

GE used some 5 layer plate material that helped, too. They used it on their 5AR4s and 8417s, as well. A copper core layer helped conduct the heat away better. Costly stuff, supposedly developed by---Texas Instruments! Manufactured by an explosive welding process. similar to making bimetal for thermostats.

Westinghouse really innovated the high Gm close spaced beam tubes. The 7591 and 8417 were both originally Westinghouse designs.  GE designed the 6550A, but the plain vanilla 6550 was a Tung-Sol design.

Tung-Sol's Chatham division made some really stout tubes, but the ultimate in "cost is no object" tube construction (besides the hand-built submarine repeater stuff) probably has to go to Bendix Red Bank. Ive run a pair of 6384s for hours at 6550-ish condtions (in a Dynaco MK3) with no issue. A few of their types were second sourced by Tung-Sol, Cetron, and most recently a mysterious company called "M U Incorporated", that has a skeletal web presence at:

http://www.mu-inc.com/

[Napalm2002]

Love tubes. And valves.very nicely done. How much do u have invested in the circuitry? Where did u get the transformers?

[c4757p]

Love tubes. And valves.

Hmm... tubes are nice, but I really can't stand valves!

[N2IXK]

Hmm... tubes are nice, but I really can't stand valves!

How do you flush your toilet?   

[calexanian]

The multilayer material used in plates came in a few different varieties. Originally tubes just had Nickel anodes. An adherent layer of powdery carbon (Referred to as black plat tubes)  had a black body radiation of about %80 to %90 in practice. Graphite was also used in early tubes. Molybdenum was used if cost would allow. In transmitting tubes graphite and other materials slowly gave way to zirconium coatings. Zirconium has multiple advantages as it will act as a secondary getter at red heat and has a good heat radiating qualities. Most graphite anodes in good tubes are coated with Zirconium. Early 5881's and other tubes from that series actually had zirconium painted in a strip running down the out side of the anode opposite of the plate from the electron beam strike area. During the war Germany started experimenting with Holland steel plated with nickel and aluminum sputtered in an extremely thin layer on the outside. After processing the aluminum layer becomes a matted Grey and even though aluminum would otherwise melt and sputter in tube conditions it does not. This product was called Aliorn. Most tube manufactures still use it to this day. In the US they added copper over the steel and nickel and aluminum over that. creating a 5 layer product. Actually in the end it was being produced in a plating process and not the explosive cladding process. Some high voltage diodes would have the copper layer bare and exposed on the inside.

[oldway]

To make a good vacuum tube amplifier, you have to have a lot of experience and knowledge, very good components and mainly good output transformers (the most critical components).

If you don't have all this, why loose time and money ?
For experience?
I don't think such experience would have some interest now and in the future ...

A vacuum tube amplifier is very expensive and has very poor energy efficiency.
It would have to be very very good to compensate this.

What are the power, distortion, frequency response?

A lot of people think all the vacuum tube amplifiers are very good, that's wrong.

There are still very good available output transformers as thoses:

http://www.ringkerntrafo.nl/shop/high-end-audio/uitgangstrafo-s/push-pull-opt.html

For good schematic, look for Marantz model 5, of still better, Mc Intosh model 30 or 60.

If you have no experience with vacuum tube technology, you should began with guitar amplifiers.
It's far more simples, as it needs only limited frequency response and there is no concern with harmonic distortion.

[N2IXK]

In a lot of cases, the use of tubes nowadays is more an aesthetic/artistic decision than an engineering one. Of course, if you are trying to generate huge amounts of RF or pulsed power with a minimal component count and simple circuitry, tubes still represent the state of the art.

A well done tube amplifier is a piece of "functional artwork", in a way. Tubes themselves are truly examples of "industrial art". They were largely handmade, to very close tolerances, and formed the basis for the electronics industry for 40+ years. The amount of engineering and material science that went into making good tubes was similar to high-end semiconductor manufacturing today.  You can often look at a vacuum tube and understand how it functions, by looking at the arrangements of grids, cathodes, and plates.  Solid state devices (particularly ASICs) are literal "black boxes" whose functionality may or may not be considered "proprietary" and/or controlled by copyrighted firmware.  Yes, they enable functionality, performance, and space/power efficiency that couldn't be dreamed of using tubes. Imagine a tube equivalent to a barebones cellphone, with a backpack full of tubes and cavity amplifiers, driving a klystron! No thanks...

But a vintage piece of tube gear has a "soul" that modern solid state stuff doesn't.  A throwback to a simpler time when the average user could maintain their own equipment, and often did. Building with tubes nowadays is more about keeping a part of our industry's history alive, and paying tribute to all the folks who laid the foundations for the stuff we take for granted today.

Keep 'em Glowing! 

[calexanian]

Its analogous to people and classic cars. A bone stock Honda is in every measurable sense better. But what is the fun in that?  O0

[oldway]

I agree but in applications where it's not irreplaceable, vacuum tube technology is such an high energy waste that it's perhaps an ecological crime to use it 

[Napalm2002]

Everyone knows that I only threw the valve thing in for all of the non USA bloggers!
I also like ball valves. Everyone dabbles in some plumbing sometimes!

[Zero999]

Its analogous to people and classic cars. A bone stock Honda is in every measurable sense better. But what is the fun in that?  O0

Same with steam trains.

I agree but in applications where it's not irreplaceable, vacuum tube technology is such an high energy waste that it's perhaps an ecological crime to use it 

Again, classic cars and steam trains cause horrible amounts of pollution but some people keep them going because they're fun.

[free_electron]

But a vintage piece of tube gear has a "soul"

 its a pile of scrap metal enveloped in glass containers interconnected with other bits of metal, carbon and paper. it's got just as much 'soul' as a pile of refined sand with some inmpurities encapsulated in black epoxy..

I also like ball valves

i will take my hat off to the first guy that can make a working ball-valve amplifier .

[calexanian]

i will take my hat off to the first guy that can make a working ball-valve amplifier .

Well, lets see. If the ball valve has pot metal and any copper on it we can get some zinc oxide and come copper oxide. Can make some crude rectifiers with that. Hmmm.... Nah, I got nothing....