A. D. Blumlein

[DaveP]

I recently purchased a copy of "The life and times of A.D.Blumlein", mainly because of my interest in the origin of circuits.

What amazed me was that he designed the attached circuit for EMI in 1932, a good 2 years before  Bell Labs paper on negative feedback.
The attached circuit not only has negative feedback but the first use of a cathode follower I have seen.  He also invented the Long tailed-pair for the first computers and this was used later for practically every guitar amp.

For EMI he designed the first TV camera circuit and the 405 line TV system, but his greatest achievement was the H2S radar system which won the battle of the Atlantic and saved the UK from the U Boat threat.

His life was cut short at age 38 because a mechanic forgot to tighten the last tappet out of the 192 on the four Merlin engined Halifax bomber he was in.  The inlet valve descended into the cylinder and the hot exhaust then entered the supercharged inlet manifold causing an engine fire.  The fire caught alight the wing tank and it burned through the wing.  When it lost the wing the plane inverted and crashed killing all 11 passengers and crew.

His work was deemed to be of such national importance, that news of his death was suppressed until the end of the war in 1945.
His contribution to the war effort was said to have shortened it by two years and saved untold thousands of lives.

DaveP

 

[emrr]

Interesting.

What is the value of the cap at the 3rd stage plate?

Can you make out all the parts values? 

Am I seeing the 4th and 5th tubes grids and plates connected?

I can't think of another output transformer connected in that manner. 

I'll have to get a copy!

 

[DaveP]

Sorry about the quality.

First tube: LS5b, 2mA. 20k dropper 2uF, 1uF to next grid 100k.

Second tube: LS5, 9mA  5k dropper 4uF, 1uF to next grid 100k.

Third tube: LS5, 10mA 10k dropper10uF dc coupled 10H coil.

Fourth tube: LS5  3090 ohm dropper to 8uF . plate res 236k.

Fifth tube: LS5 68mA total. 53 ohm dropper to 4uF, then 25H coil and another 4uF to OPT 500 ohms sec.

tube one IPT sec fed from 100k from -8V
tube 2 from -27.5V
tube 3 from -48.5V
tube 4 from -11V.

7 sept 1932

Hope that helps!

DaveP

 

[PRR]

Re/De-generation was known from old.

A number of people saw advantage in degeneration.

That 1932 amplifier is not novel, but unusual, and unusually brave to take NFB around three gain-stages with L-C coupling. (Hard to imagine it has high NFB.)

Black was not accepted at first. What he did was found a general theory of NFB, and apply it to a specific business problem (telephone repeaters). Eventually he was acclaimed inside his organization, then generally, perhaps more than he deserved (AT&T had a hot PR department once). But we needed the work of Bode and Nyquist and others to fully understand the stability problems.

 

[JohnRoberts]

I think Black was credited with inventing NF in 1927 but didn't completely grok the stability issues. I think the concept was kicking around informally and known by others, some who may have actually figured out how make it useful. The real history is a little sketchy and hard to pin down. Without NF the telephone systems wouldn't have worked worth squat, and the very early ones didn't.  :

That said success has many fathers and they had patent lawyers even back then.

It was a pretty small industry back then. My dad worked at Vitaphone  (joint venture between warner brothers and western electric) around then (late 20s) on the first sound movie (Don Juan). I think he was at WE before Vitaphone, later in the 30s I know he travelled to UK to do sound recording for the coronation of King George(?). Probably for newsreel shorts. The best I can piece together he worked for several iconic companies (including RCA and even Muzak), but like I said the industry wasn't that big. 

JR

PS: I thought Blumlein was known for inventing stereo?

 

[pucho812]

JR

PS: I thought Blumlein was known for inventing stereo?

Yes  one of his many accomplishments was stereo recording technique at the Hayes factory.

 

[ruffrecords]

Yes  one of his many accomplishments was stereo recording technique at the Hayes factory.

There is a story about a meeting between EMI and a certain US company that had a patent on a method of recording stereo records. Apparently the US company wanted a royalty from EMI for all their stereo records and they showed EMI their patent of the technique. EMI prmptly took out their own patent of the same system , granted a few years prior and asked the US company for a royalty on every stereo record they sold. How much of this is true I do not know.

Among his other achievements were:

The moving coil cutting head
Coincident velocity  pair for stereo recording
Using hybrid transformer to encode decode mid/side signals
The ultra-linear amplifier

Cheers

Ian

 

[Pip]

Yes a fascinating read, tech geek nirvana. I read it when it first was published.  He was also a really nice guy!

 

[Tubetec]

I had no idea that he died so young and so tragically , I probably should read more of him .

 

[guavatone]

I’m sure it’s a good read. Seems he had a way with geometry in his electronics.

Probably doesn’t talk about his sexy cross dressing until here:
https://www.tubecad.com/2009/04/blog0163.htm

It’s a shame he died young. Our tech universe would have been shaped different, by such a brilliant visionary.

 

[DaveP]

The attached schematic is from a Crosley Radio output stage from 1960, well before TubeCad.

DaveP

 

[guavatone]

Sexy!  i’m Curious if the garter circuit works well for P-P followed by an output transformer. He probably would have went with cheap sand if it was a good option though.

It’s a different type a garter though. The above is the screens and the tubecad is grid to cathode


Without Blumlein, we wouldn’t have what I think as one of the best recordings. VM Bhatt and Ry Cooder meeting by the river. Or it wouldn’t have been as spectacular.

 

[DaveP]

It’s a different type a garter though. The above is the screens and the tubecad is grid to cathode

Look again, its grid 3/cathode to opposite grid.

DaveP

 

[merlin]

Probably doesn’t talk about his sexy cross dressing until here:
https://www.tubecad.com/2009/04/blog0163.htm

Blumlein had nothing to do with the 'garter' bias circuit. Broskie got his wires crossed somewhere.

 

[Whoops]

Thanks Mr Blumlein for the Pan Pot Law!

 

[L´Andratté]

Wow, what a life. So "live fast & die young" also applies to EEs!
I guess it´s a must-read, will order today, I love interesting biographies.
Thanks for posting, Dave !