Every once in a while, I stumble on something really amazing that I have to pass along. Perhaps a few of you have already enjoyed this, but what the heck:

In 2006, Claude Perrier, F2FO, celebrated the centennial of the invention of the triode by crafting a dozen in his own shop. Lee DeForest invented the original, but Claude chose to follow a refined design from 1915, the General Ferrié TM. Click this link to watch him work on this fascinating project and read the mangled Googlefrancais here.

I've known quite a few engineers over the years and I've seen a great deal of complex and imaginative builds, but nobody made their own tubes. Skilled as he is, I still do not see Claude whipping up a batch of FETs in his shop. :0)

That's damn cool! The beauty of the valve is one can actually see it on a human scale!

The tube really is something of an art. It's a combination of very basic things, vacuum, forming metal and glass, fundamental electric theory, all packaged to do something.

Should we get blown back to the dark ages, one could pick up a tube and see it, grok it, build more of it, etc...

Looking at a microchip does not work the same way. To leverage that technology, one needs an enabling technology in place first! That means it's not a core thing, directly leveraged by humans.

With a tube, that all can be observed, function known, and applied almost completely by direct observation.

Makes me think of vinyl -vs- CD in a way too. The tech in vinyl is basic. One makes changes to a material, then drags something through there to reproduce sound.

On a CD, one asks a machine to do the same.

The latter is more repeatable, less noise, etc... It also takes a ton of people, energy and understanding to jump start, then continue.

The former can be done by most anybody (and started that way), in their shop, applying the basics of craftsmanship to the problem to reach a solution. It's not so repeatable, takes more labor, but also can just be done because one person wants it done.

Reminds me of the Star Trek episode where Kirk and Spock get stuck in 1940s-era America and Spock tries to build some kind of tricorder circuit using vacuum tubes...

I liked that one!

That is probably one of the most noted episodes due to the guest star Joan Collins (Edith Keeler).

While attending college, I found a really neat book in our library on the early history of the vacuum tube. Before about 1930, there were some very crude-looking handmade tubes in production. The book had a photo of such a tube from Japan.

Earlier today, I was looking at some photos of 1930s era CRT manufacturing. That process was also very labor intensive and required people with highly specialized training. The early round CRTs were hand-blown into a mold! Take a look at http://earlytelevision.org/14ap4_construction.html

Great stuff everybody! It has been awhile since I spieled, but this topic has me going. I truly believe that human beings are hardwired to adore a certain amount of third harmonic distortion. I do not have a concrete scientific explanation. Perhaps it is simply hoodoo, but history has shown that there is still no solid reason to abandon a really good thing.

Like analog tape and ribbon microphones, those heralding the complete demise of tube technology are simply not informed. A good tool really never loses the ability to be useful. You may not have a warm glow in your Zune or iPod, but the tunes you spin from any era often have them in the signal path. Yes, even today.

Of course, most great instrument amplifiers are still full of firebottles, but lots of products go further than simply making stringed things scream, or get crunchy, warm and smooth. Technology has created all sorts of hybrids, updates and quieter versions of old standards. As a result, many other current tools of recording still rely on valves.

Tube microphones are still produced in quantity by longtime manufacturers like AKG, Neumann, Gefell and Oktava. Relative newcomer, Audio-Technica, has a couple of LDC models that run on 48V phantom power like any other condenser. They are very popular.

Some brands use outsourced components or machining, but make them in the good old USA. Peluso and Mojave come to mind. Heck, you can even build your own from a "banjo mart" special. The article by David Royer jumpstarted the main Chinese manufacturers -- 797, Felio and Alctron -- into making piles of different relatively inexpensive tube mics to varying degrees of success.

The late great Bill Putnam is often called the father of the recording studio. He was a Dad too, and his sons have turned Universal Audio into their own little empire using updated versions of his preamplifier designs.

Located in Portland, Sours makes top custom gear and Hamptone produces a highly regarded and popular tube preamp available assembled or in kit form. Outside of our neighborhoods, many manufacturers make tube preamplifiers from the crystalline colorless Avalon to the venerable "Heathkit of Music" designs at PAiA.

When it comes to tube compressors, limiters and equalizers -- like anything else -- there are plenty of Chinese made models to explore at the mall. At the other end of the spectrum, the current offerings from Fearn, Drawmer, Summit, Pendulum and Manley are among the best in the world.

Believe it or not, huge hit records are still made on tube mixing desks too. Three different models are available from TL Audio alone. This video tour from the 2007 AES convention shows that the latest stuff from Tegeler Audio is amazing. Touted as the first all tube mixer, this monster will never make anyone forget the REDD desks at Abbey Road, but what a concept!

It seems that the robotic motions of the music machine have made the whole industry seem vapid, computerized and inorganic. Sure, there are plenty of products with starved plates and amber LEDs glowing, but there are also many current offerings of high quality and incredible design. The vacuum tube may have become specialized, but it still has a firm hold on musician, producer, engineer and listener alike.

I'll bet that the monster Vintec mixer, which has 1539 tubes, really warms up the room that it is in!!

I have also heard about those phantom-powered tube microphones. How do they do it? Phantom power is pretty wimpy--at best, you can deliver approximately 196 mW of power to the mic's circuitry.* What kind of vacuum tube has a heater that will operate on such a small amount of power?

* The official phantom power setup is a 48V supply, fed through 6.8k Ohm resistors to each leg of the balanced pair. Thus, the phantom power source looks like a 48V source with an output resistance of 3.4k Ohms. For maximum power transfer, your load would have to be 3.4k Ohms.
Calculation:
48V/(3400+3400)=7.06mA
7.06mA*48V=338.3mW
Half of this is dissipated by the load.

" What kind of vacuum tube has a heater that will operate on such a small amount of power? "

Some early 50s hearing aid tubes ran with as low as 12.5 mw heater power! The Ck-512AX, for example ran the directly heated cathode at 0.625V and .02A. The output tubes for these devices (Ck-549 ??) used the full "A" battery voltage of 1.25V @ .02A. It should be possible, with proper DC/DC converter to power tubes like that with phantom power.

Good picture of 2 of these little tubes here on a TRANSISTOR site:

http://www.ck722museum.com/page3.html

Wow! I'm impressed!! I didn't realize that it was possible to get a usable amount of electrons with that small an amount of heater power! It would really be cool to experiment with subminiature tubes! I wonder, where do the tube condenser microphone manufacturers get their tubes?

The spec sheet for the A-T 3060 says that it only draws about 3ma from the 48V phantom power (144 mw). I don't know what tube they use. The early hearing aid tubes were pretty noisy and could be somewhat microphonic.


http://www.audio-technica.com/cms/resource_library/literature/05da3af13ca5b023/a t3060_english.pdf

Thanks to everyone for ringing in on this topic!

As far as I know, the Audio Technica 3060 uses a NOS Raytheon 6418. I believe this is also known as a 548DX.

This Herbie fellow has created a very interesting solution to tube microphonics.

Oktava builds the MKL-2500 around the 6C315P, but some folks have had success by replacing it with a 6AK5.

The original AKG C-12 was based on a 6072, as were the later redesigned Telefunken versions known as the Elam 250 and 251. Domestic models came with a standard German AC701.

A modern classic, the Groove Tubes MD-1 was similarly designed around a 12AX7/12AY7. Many tube microphones of the past and present either use a 6072/12AY7 or can be retrofitted with one. (A very popular Electro Harmonix microphone preamp is simply known as the 12AY7.)

The Neumann U-47 uses the impossible to find Telefunken VF14. In 1969, the company addressed the shortage of replacement tubes by recommending a solid state option. Many U-47 microphones have since been retrofitted with 13CW4 Nuvistors, but fixing the impedance mismatch takes further modifications. Fortunately, the U-67 was built around the much easier to find EF86.

Korby is among the best manufacturers to discover the magic of the old microphone designs. While insanely expensive, they make an amazing tube microphone right here in the good old USA:

The KAT System is the first hot-swappable microphone capsule system of its kind to incorporate a matrix connection that will accept both the Neumann style center contact and the AKG style floating diaphragm. Available with 251, C12, U67, U47, and C800 head assemblies. The heads are truly hot-swappable and can be removed without the use of tools while in session.

Long live the triodes!

I'm impressed and somewhat amused by the Raytheon 6418. I'm impressed that a vacuum tube could be built that only uses 10mA of heater current at 1.25V. I'm amused that somebody would dare call this a "power" pentode, since the maximum output power of this device is about 3mW!

Looking at the spec sheet for the Audio Technica, I was a bit surprised that the frequency response of this microphone is not as flat as that of many lower-cost condenser microphones. Was this thing intended to be used specifically as a vocal mic, in which case the upper-midrange "presence" peak and bass rolloff are intentional?

6418 curves and spec show around 12% distortion (3rd harmonic) and up to 20% (second harmonic) and yet this tube is used in a high quality audio device ????

Price of the 6418 in the 1971 Allied industrial catalog was listed as $3.90 ea, down to $3.34 in lots of 50 up... Wonder what they sell for now ?

The datasheet doesn't help very much in predicting what kind of distortion figures would be obtained when using this tube in a microphone application. The test conditions shown swing the grid from about 0V to about -2.4V (850mV RMS sine wave + -1.2V grid bias). -2.4V is almost enough to cut off plate current completely, according to the characteristic curves. Are there any vacuum tube distortion experts in the house??

Was this thing intended to be used specifically as a vocal mic, in which case the upper-midrange "presence" peak and bass rolloff are intentional?

Absolutely! The benefit of most LDC tube microphones -- intentional or not -- is a "chesty" effect. In this case, it was engineered into the design.