The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all products and all products

    Did you ever wonder who invented stereo?



    Posts : 304
    Join date : 2010-02-03
    Location : Costa Rica

    Did you ever wonder who invented stereo?

    Post by baddog1946 on Thu Oct 13, 2011 8:10 am

    This is a book review by "John Atwood" about the inventor of stereo for the history buffs among us. A bit long but very interesting. I have just finished the book and it is worth a read for sure.

    What happens when history falters? When brilliance is forgotten? When a brilliant mind dies tragically in obscurity and secrecy? This is essentially what happened to Alan Dower Blumlein, a British electrical engineer who developed many circuits and concepts we take for granted today, yet is barely known. This obscurity was compounded by a confluence of bad luck and unfortunate behavior which delayed the first biography of Blumlein until 57 years after his death. I’ve just finished reading one of the two biographies that appeared in 1999: The Inventor of Stereo: The Life and Works of Alan Dower Blumlein by Robert Charles Alexander.

    Blumlein was truly an electronic genius, at least at the same level as Edwin Armstrong, yet had the bad luck of working in a company (EMI) that didn’t encourage publication (Blumlein only published two papers in his career) and discouraged publicity (only four photographs of Blumlein are known to exist), and died while working on an extremely top-secret project (centimeter radar) during World War II, resulting in his war work being buried in secrecy. His only tangible legacy (other than his designs and inventions, which were widely used) were his patents - over 120 of them - which trace the path of his short career.

    Here is a thumbnail summary of Blumlein’s life and accomplishments: He was born in London in 1903 of an Alsatian father and South African mother (of Scottish background). He was an intelligent child, but only learned to read at age 12 when he realized this was important. He picked up an interest in electricity as a child, which lead him on a path to a degree from City and Guilds College in London, a respected technical branch of Imperial College. In 1924 he got a job at International Western Electric (later to become S.T. & C.) analyzing telephone line cross-talk. As part of this work, he invented a balanced bridge that allowed sub-picofarad capacitance measurements on phone lines, which greatly facilitated efforts of cross-talk reduction. He also developed very sophisticated compensation networks for buried and undersea cables.

    In 1929, Blumlein moved to the Columbia Grammophone Company, where he developed a moving-coil record cutter as a way to get around Western Electric’s expensive electrical recording patents. He then developed the HB1B moving-coil microphone, widely used by EMI and the BBC. While working on electrical recording techniques, Blumlein started working out how to record and reproduce the directional aspect of sound. Fortunately, his general manager, Isaac Shoenberg, gave Blumlein and his group the resources to pursue this to point of not just conceptualizing “binaural” sound (the word “stereo” didn’t really become common until the 1950s), but creating and building an entire system including microphones, 45-45 degree record cutters and reproducers, binaural sound on film, and binaural mixing and equalizing networks. Blumlein was not working alone on this; he was one of a talented team, but he had both the overall vision of the concept and the intelligence to implement details. He was well-liked by his co-engineers and spent the time to explain his ideas to them. Although he applied for patents for the binaural system in 1931, by the time they actually were taken up for everyday use in the 1950s, the patents had expired! This is just one example of how far ahead of his time Blumlein was.

    In 1931, HMV (”His Master’s Voice”) and Columbia Grammophone merged to become EMI (”Electric and Musical Industries”). Isaac Shoenberg’s talented development team, which included Blumlein, thus became available to this larger conglomeration, which included access to the American RCA patents (via HMV, which was connected to Victor, which had just been bought by RCA in 1929). The “new big thing” in the early 1930s was television. The BBC had been doing experimental TV broadcasts since 1932 using the crude Baird mechanical system. HMV had been working on an all-electrical system, with help from RCA. The merger brought Blumlein into the television effort, and he quickly began solving practical problems with clever circuits, many of which were passed back to RCA. They included: perfecting the merged sync and picture signal, DC restoration techniques, the “efficiency” flyback scanning circuit using a damper diode, the cathode follower, the differential amplifier (his term was the “long-tailed pair”), equalizing filters using tapped delay lines (a precursor to today’s digital FIR filters), improved coaxial cables, negative feedback around pentode amplifiers (preceding Bell Labs’ work in this area), the slot antenna, the “ultra-linear” power amplifier circuit, and many more. This was Blumlein’s most productive period in his life.

    Although EMI was rapidly perfecting an all-electronic television system, Baird clung to his mechanical system and was very vocal in pushing his ‘all-British’ system. In order to diplomatically break this impasse, the Postmaster General proposed a Television Committee, which, after reviewing the technology in the U.K., the U.S., and Germany proposed that the two competing organizations, Baird Television and Marconi/EMI both transmit on alternate weeks for a three-month trial period at the end of which the superior system would be selected. The technical requirements were for a “high-definition” system of at least 240 lines. Both Baird and Marconi/EMI were given space in Alexandra Palace, a 19th century building located on one of the highest points in London. Each group had their own studios and television equipment, but shared a 45 MHz BBC transmitter and antenna. Baird stuck with the minimum requirement of 240 lines and used a semi-mechanical system with electrical help from the American Farnsworth/Philco technology. EMI went out on a limb and proposed a 405-line system, higher than any system under design at the time. This was risky, but Schoenberg trusted his crack design team lead by Blumlein to overcome the technical hurdles.

    The two television teams, Baird and Marconi/EMI, designed their systems and started to install equipment into Alexandra Palace in 1935. By the Radiolympia radio exhibition in August 1936, both teams were ready to broadcast. There were a few glitches, but both managed to get on the air for the event. The official three-month trial period began in November 1936. It was clear from the start that the EMI system was superior to Baird’s, both in quality and in operational reliability. In 1937 the BBC selected the 405-line EMI standard, continuing the broadcasting that started in 1936. In order to get this entire system working with all the diverse bits of technology was an immense task, but EMI and Marconi did it, with a robust system that continued to be used up until the 1980s. When the RMA in America proposed RCA’s 441-line television standard in 1938, most of the technical details came from EMI, although RCA would be loath to admit it. Regular broadcasting in America didn’t begin until the 1939 Worlds Fair, and even then, it was classed as “experimental”. The NTSC standard wasn’t finalized until 1941, although this five-year lag from the finalization of British standards allowed it to incorporate a few improvements, such as 525-lines, equalizing pulses, FM sound and negative picture modulation.

    As the problems with television got sorted-out and World War II loomed, EMI began to get involved in acoustic aircraft tracking leveraging off of Blumlein’s binaural work. Being viewed as just a consumer electronics company, EMI was not considered qualified for the top-secret British radar work then going on. However, they were associated with Marconi, who was building early klystrons and magnetrons, and word got back to Blumlein’s team on some of the radar work. When EMI voluntarily improved some early radar prototypes, they were reluctantly brought into the radar effort. This reluctance ceased when the incredible productivity of Blumlein and his group became appreciated. Eventually EMI got the contract for the H2S microwave radar initially designed for bomber navigation. However, H2S became famous as the aircraft radar that was instrumental in spotting German U-boats, severely crimping the U-boat campaign.

    While testing a cavity magnetron version of the H2S system in a Halifax bomber, Blumlein and several other members of his design team were killed when the plane crashed in the Welsh countryside on June 7th, 1942. Magnetron radar was a deep secret, and this crash was hushed-up. The only working H2S prototype as well as the people who designed it perished, setting back the British radar program. EMI eventually got the design back on track, but the loss of Blumlein was acknowledged by Winston Churchill as a national tragedy. Several of Blumlein’s patents still in the pipeline were issued under his wife’s name as executor.

    Periodically in the 1950s, 60s and 70s articles in the British technical press would remember Blumlein and his incredible work, but biographical details were scarce and often wrong. Several biography efforts were started but never finished, the worst being Francis Thomson’s hoarding of historical material for decades without allowing access. Luckily, Robert Charles Alexander was able to interview people who knew Blumlein while they were still alive, get access to EMI’s corporate files, and have the engineering knowledge to analyze and evaluate Blumlein’s patents. From a literary point of view, Alexander’s biography of Blumlein does not have the best writing quality and is overloaded with an excessive amount of details, but as an engineer and student of technical history, I overlooked these problems, and found the book to be intriguing, mainly because of Blumlein’s fascinating life. Alexander does a good job of documenting Blumlein’s personal life, mainly through reminiscences of his wife and co-workers. A rather large section of the book is dedicated to documenting Blumlein’s death in the June 1942 crash in Wales. Although a gruesome though intriguing story, part of the reason for this excessive amount of detail is that Alexander had access to previously classified material that clarified the cause of the crash (a loose rocker-arm adjustment nut) and dispels the rumors of the crash that developed over the years in the absence of any real information.

    Alexander describes all of Blumlein’s important patents in sufficient detail for an engineer like myself to understand. This will likely go over the head of the casual reader, but is still important, since the brilliance of Blumlein’s work is best appreciated by knowing these details. The list of all 128 of Blumlein’s British patents is given in the appendix, and the publisher has a website that has the texts of many of these patents. Unfortunately, only a few have the drawings, and not all patent texts were entered, with the project apparently abandoned in 2001. In an effort to find out more about the patents, I started doing internet searches. I was only able to find two of the British patents, but searching on Google Patents and Delphion, found that there were U.S. equivalent patents for essentially all of the British patents, and was able to find and download 72 of them. (An aside: searching Google Patents is a real pain, since key words are highly garbled and patents are missing from their database.) They are fascinating reading, and will likely be the source of future Clarisonus postings.

    Alan Blumlein made vital inventions in the area of audio, television, radar, and associated fields of electronics, yet was nearly forgotten. I highly recommend anyone interested in the history of electronic technology to read his biography and dig into his patents.


    Posts : 14
    Join date : 2010-11-25

    Re: Did you ever wonder who invented stereo?

    Post by quad on Thu Oct 13, 2011 1:58 pm

    Excellent post. Thanks!

      Current date/time is Wed Sep 28, 2016 2:47 pm