Anyone ever used a WE416B?

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

bcarso

Well-known member
Joined
Feb 20, 2005
Messages
4,055
Location
San Fernando Valley, Los Angeles
http://www.westernelectric.com/spec_sheets/416B.pdf

Gm of 50mA/V, µ of 200 (!). And useful out to around 4 kilomegacycles, as they used to say in the 50's. Might be something of a challenge to tame parasitics :roll:

I'll bet it's scarce. And microphonic. I found it re-reading an excerpt in pdf from Gewartowski's book, kindly posted by PRR about a year-and-a-half ago in here, in a CJ preamp thread:

http://frank.pocnet.net/other/docs/PoET/PoET_05.pdf

EDIT: Available for about 11 bucks. Must be hard to find sockets etc. though.
 
Ceramic triode. Has no "glow".

I know I have figured this tube before. Try Search.

I believe the ratings require forced-air cooling. It goes in a transmission line. Air is forced through the line via 1/4-wave stubs or sumthing.

http://www.tubecollector.org/416b.htm
 
According to 7N7 in the diyAudio forum, the 416D was even a little better---probably a selection out of lots of nominal 416s that had better grid winding uniformity and optimized grid-cathode spacing. 7N7 mentions 65 [mS] and µ of 250, and comments "a nightmare to install and run..."

You may be right about cooling---although the dissipation is not terribly large, the spec does have some pretty low numbers for certain maximum temperatures: max grid seal temperature 100 degrees C!
 
Yes, in a radio telescope I built in high school. The tube is designed for mounting in a waveguide. A threaded ring is the grid connection as it was mostly used as a cascode input 1st RF preamp in cross country microwave systems. The tube construction is glass and brass with kovar seals between the sections. All the metal parts are gold plated. The tube is small and low power so convection cooling was adequet. It has a relatively high gain and a very low noise figure (>150 deg. K). It should be much less microphonic than an ordinary triode as the grid was made of wires stretched at high tension across the face of a ring.

I think there have been some audio uses, specifically phono preamp stages.

Here is a link with a picture:

http://triodeguy.com/416b_phono_stage.htm

Not my first pick of a tube for audio use as the packaging makes it difficult to work with. Supply should be good as it was the amp used in those big horn antennas that you used to see on the tops of telephone company buildings.
 
Most interesting. Thanks for that link.

I wonder how bad the flicker noise is on these?

Evidently grid wires are wound at quite high tension as a rule, at least for high-performance tubes---one ref stated that the tension was typically about 1/2 of the breakage value. I'm wondering if the microphonics I see in the 6C45 are actually due to the whole grid structure vibrating, rather than the individual grid wire segments. It would seem as if the structure would be better damped though.
 
> The tube construction is glass and brass

You are correct. I was thinking of another little lump. The 416 is more brass than glass; can you see the cathode "glow" through the top or side seals?

> it was mostly used as a cascode input 1st RF preamp

Documents I found (can't share) for the "B" version clearly show it as a high-level device, not an input device. At ~4GHz you can get 10dB power gain at 65mW out, or 5.5dB power gain and 570mW out, or triple from 658MHz to 2GHz at 170mW out: these are larger powers than preamps need.

Unverified plots suggest a 16dB noise figure at 4GHz, which really bites your power budget (you need 20 times more sending power than you could use with a 1dB NF input). I would guess that microwaves went to a crystal mixer and immediately down-converted to some lower frequency where a common tube can have a decent noise figure. The crystal mixer's 4GHz NF should be lower than 14dB, and a good hot tube can touch 6dB NF at say 400MHz first IF frequency.

Also: "the tube's primary application is as a large signal amplifier... no manufacturing controls...to ensure the small signal performance..."

We know the BTL Allentown labs were not dirty barns, just because you can't hold 0.00165cm spacing without obsessive cleanliness. Probably 99% of tubes will be as pure as the Allentown snow (well, the snow was cleaner in the 1950s, before half of NJ moved out there). But no promises from BTL.

Note that TriodeGuy is working the 416 at about 4mA, instead of the 30mA where the fantastic Gm is cited. I can not find Ik/Gm plots (you don't starve a tube making 4GHz) but 50mMho at 30mA is likely to be 18mMho at 4mA, or 55 ohms cathode impedance or 140 ohms noise resistance. Great for phono, "high" for transformerless 150 ohm microphone.

Also the input clipping is 0.2V at 4mA (0.6V at 30mA), low for modern studio mikes.

18mMho at 4mA is 4 or 5 times better than paralleled 12AX7 working at the same 4mA total.


> Evidently grid wires are wound at quite high tension as a rule, at least for high-performance tubes

Not so for low-performance tubes. 6J5 grid is soft and cushy. You can only take loose winding so far, then they use the "Frame Grid" buzzword. 416 pushed this concept to or past the practical limit. The logical next step is to make your "grid" as the atomic surface of a crystal junction. And that leads to the idea of a solid on both sides of the "grid", modifying the annoying (yet useful) space-charge in the grid-plate space. But "glow" is lost.
 
It would be interesting if modern techniques could somehow make the cathode surface vary in shape under the grid to combat inselbildung.

The phono pre probably was running at lower current to reduce flicker noise, as according to Cherry and Hooper that tends to go directly as the plate current. And it would be especially important with RIAA shaped gain.

When I rolled a crossover/EQ with SN7's and wanted to minimize coupling C count I wound up with a boatload of low frequency noise. There was a large amount of bass boost required that continued down to about 30Hz and a fair amount of gain, so it was already a circuit that cried out for quieter devices. However the man wanted devices that glow.

I now realize that, in addition to combatting the noise by reducing currents I should have made sure the heaters were biased a bit positive w.r.t. cathodes, as I think those spurious currents were contributing some of the excess noise, especially with the probably-not-so-clean Sovtek tubes. I don't have it to tinker with now, nor the time to do so.
 
The 416 was developed in the 50's for use in the AT&T backbone microwave system. It was mainly used in the TD2 radio, as one of 3 cavity amplifiers in both the transmit and recieve side of the radio. Also use in the Mic Gen to generate the microwave signal. The grid is not a spiral like regular tubes, but is a very fine mesh made of wire so fine that it makes a human hair look huge. It is a planar tube and all the elements are very closely spaced to cut down on transit time. The plate connector is a little nub that fits into a friction fit connection. To install into the cavity properly required a special KS tool that tightened onto the base of the tube so you could insert it into the cavity and screw it in. The socket plug was non-standard too.The 416D would provide about 5 watts output at 4 GHz. I spent 20 years working with TD2 and TH3 radios both doing bench alignment and outside plant radio crew, until AT&T scrapped all microwave systems and replaced them with fiber. The 416 was another example of the engineering prowess of Bell Labs and the manufacturing ability of Western Electric, to create very specialized products that worked incredibly well under the most adverse conditions.

Jim Zuehsow
 
OT: stll working on the Larrchild output trans for the 407A.
The big core didn't work, so going for a "build out"
In other words, two transformers instead iof one, the first is a 1: 4 and the second is a 1:10, so you get a 40:1 transformer, only without all the phase shift, resonance, which is cool, becuase there is a feedback winding in there.

Put it all in a black box, and nobody will know.
Usually this is reserved for IF freqs, but lets try it on audio.
 
Sorry, 10:1, forgot the root.

:oops:
been a while.

47 nites in my tent this summer. thats a record. I was thinking if subleting my apt on the weekends!

yeah, the 10:1, too much phase for a tert winding.
 
> make the cathode surface vary in shape under the grid to combat inselbildung.

Same problem which causes inselbildung in the first place. The ideal "grid" would be a plane surface. Grid wires can not be zero size, zero pitch, zero error, so can't be plane. Trying to correct their non-planeness with a lumpy cathode seems doomed. The grid errors are already at the fabrication tolerances, the complementary errors at the cathode are even smaller, and I don't see how if grid imperfections are a problem, cathode bumping won't be a larger (i.e. smaller) problem.

> if modern techniques

Well yeah. If you can write "IBM" on the point of a pin, as is done now by moving individual molecules around with an electron microscope, you could fabricate a much finer grid than WE could with highly refined versions of jeweler's techniques for working fine bits of metal. I believe modern CPU photolithography (electron beam?) techniques make finer structures than 416 grids. Flash aluminum on a wafer, mask a grid, etch the holes, dice to 416 size, then etch the silicon off the back. Walla, micron grid structure. Or cover the grid with thin SiO, etch most of it away, fill it with sugar, spray cathode oxide, flash with nickel, and wash the sugar out: complete grid-cathode structure with reproducible dimensions unimaginable in 1950.

> The phono pre probably was running at lower current...

Well, maybe just because guys who do 1mA-3mA on common receiving tubes can't wrap their mind around a 30mA tube. If you pencil 100V headroom above the plate, the plate resistor is 100V/30mA= 3K. Total power is like 10W. That's just strange for hi-fi work. And in fact there's no reason to drive a phono preamp down to 50 ohm noise resistance... it seems to be a moving-magnet preamp, pickup has ~5K dead resistance already. In part because the 5mV/47K pickup standard evolved for "good" noise performance with common Gm=1,000uMho (Rn=2K5) tubes.... not a lot to be gained with higher Gm.

> To install into the cavity properly required a special KS tool.... socket plug was non-standard too

Yeah, but for audio and DIY you would just use hose clamps and tack-solder the base pins. We aren't concerned with keeping the plate tank super close to the actual plate, or grounding the grid, or 99.9999% up-time among tens of thousands of units out in the field.
 
"...complete grid-cathode structure with reproducible dimensions unimaginable in 1950."

Yeah---that's the idea. And while one was at it, do something to improve the energy distribution of the electrons emitted. Carbon nanotubes mayhap? Good cocktail party banter when you've located a fellow nerd and given up on anything more social occurring...

I'm going to have some real data pretty soon on the flicker noise stuff---not with a 416 but a more manageable relative, the 6"C"45pi. I tried a rough air-board last night and realized quickly how hard it is to work without some really quiet HV bench supplies, among other things. But with a little ingenuity I wound up concluding that 1/f wasn't terrible at ~17mA, and Gm quite healthy. And the microphonics are not really as bad as I thought---it takes a serious tap to induce significant ringing.

Pondering, I think the problems with excess low frequency noise in an earlier circuit were not the tubes but excess noise in a resistor string excited by a current source, part of an attempt to d.c. couple beyond any rational bounds. Had the parts been wirewound things would have been much better I'll bet, although ~1Mohm wirewounds are a bit exotic.
 
I made a vhf preamp for 144 Mhz out of a 416B in high school.
Although it worked well, it had some odd "super settings" that in hindsight, may have been the tube on the verge of oscillation, acting like a parametric amp.

Cool gold color!

CJ, we'll both get to the end of that project, I'm sure.
No worries.
 
i saw that trash talkin over at rem,
words like "flake....a--hole, poser....loser...."
thanks a lot, pal.
:razz: :grin: :razz: :grin:
this was all your idea, you SOB!
:grin: :razz: :grin: :razz: :green:
meanwhile, back at the winding machine...
 
Back
Top