Alan Dower Blumlein ( / ˈ b l ʊ m l aɪ n / ; born June 29, 1903; died June 7, 1942) was an English electronics engineer known for creating many important inventions in telecommunications, sound recording, stereophonic sound, television, and radar. He received 128 patents and was regarded as one of the most important engineers and inventors of his time.

He died on June 7, 1942, at the age of 38, during a secret test of an H2S airborne radar system under development. The Halifax bomber he was traveling on crashed at Welsh Bicknor in Herefordshire, killing everyone on board.

Early life

Alan Dower Blumlein was born on June 29, 1903, in Hampstead, London. His father, Semmy Blumlein, was born in Germany and later became a British citizen. Semmy was the son of Joseph Blumlein, a German man of Jewish heritage, and Philippine Hellmann, a French woman with German ancestry. Alan’s mother, Jessie Dower, was Scottish. She was the daughter of William Dower, who was born in 1837 and traveled to South Africa to work with the London Missionary Society. Alan was baptized as a Presbyterian. Later in life, he married in a Church of England parish church.

At the age of seven, Alan showed early signs of his future career. He gave his father an invoice for fixing the doorbell, signed “Alan Blumlein, Electrical Engineer,” with “paid” written in pencil. His sister said he did not learn to read well until he was 12. Alan responded, “No, but I knew many quadratic equations!”

After leaving Highgate School in 1921, Alan studied at City and Guilds College, which is part of Imperial College. He earned a Governors’ scholarship and joined the second year of the program. He graduated with a First-Class Honours BSc two years later.

In mid-1930, Blumlein met Doreen Lane, a teacher who was five years younger than him. After two-and-a-half years of dating, they married in 1933. Before the wedding, Doreen was warned by friends that some of Blumlein’s peers joked about his intelligence. They called it “Blumlein-itis” or “First Class Mind,” meaning he preferred to associate with people who were highly intelligent. Joseph B. Kaye, a recording engineer and Blumlein’s best friend, believed the couple was well-suited for each other.

Career and inventions

In 1924, Blumlein began his first job at International Western Electric, a part of the Western Electric Company. The company later became International Standard Electric Corporation and eventually Standard Telephones and Cables (STC).

While working there, Blumlein studied how the human ear responds to different sound levels and frequencies. He used this information to create the first weighting networks.

In 1924, he published one of only two papers he wrote for the IEE, about measuring high-frequency resistance. This work earned him the IEE's Premium award for innovation. The next year, he co-wrote seven articles for Wireless World with Norman Kipping.

Between 1925 and 1926, Blumlein and John Percy Johns improved a device called a loading coil, which helped reduce signal loss and interference in long-distance telephone lines. These improvements were used until the end of the analog telephone era. The same team also invented a better type of AC measurement bridge, known as the Blumlein Bridge and later the transformer ratio arm bridge. These inventions led to Blumlein’s first two patents.

His work at STC led to five more patents, which were awarded after he left the company in 1929.

In 1929, Blumlein left STC and joined the Columbia Graphophone Company, reporting directly to general manager Isaac Shoenberg. His first project was to develop a new method for cutting records that avoided a Bell patent on a moving-iron cutting head. He invented a moving-coil disc cutting head, which improved sound quality and avoided the patent. He led a team that included Herbert Holman and Henry "Ham" Clark, and their work resulted in several patents.

In early 1931, the Columbia Graphophone Company and the Gramophone Company merged to form EMI. New research labs were set up at Hayes, and Blumlein was transferred there on November 1, 1931.

During the early 1930s, Blumlein and Herbert Holman developed a series of moving-coil microphones used in EMI recording studios and by the BBC at Alexandra Palace.

In June 1937, Blumlein patented the Ultra-Linear amplifier (US Patent 2,218,902). This design used a tap on the primary winding of an output transformer to improve amplifier linearity. By placing the tap at specific points, the amplifier combined features of triode and pentode designs.

Blumlein may or may not have invented the long-tailed pair, but his name appears on the first patent (1936). The long-tailed pair is a type of differential amplifier that became widely used in vacuum tube circuits and is still common in modern integrated circuits.

In 1931, Blumlein invented what he called "binaural sound," now known as stereo sound. He and his wife were at a movie theater when he noticed that sound systems only had one set of speakers, making it hard to match sound to actors on screen. He proposed a way to make sound follow the actor’s movements.

He shared his ideas with Isaac Shoenberg in late 1931. His earliest notes on the subject date to September 25, 1931, and his patent, titled "Improvements in and relating to Sound-transmission, Sound-recording and Sound-reproducing Systems," was filed on December 14, 1931, and approved as UK patent number 394,325 on June 14, 1933.

The patent included many stereo-related ideas, some still used today. These included:
– A shuffling circuit to keep directional effects when using stereo speakers instead of headphones
– A method of using two velocity microphones at right angles, now called a Blumlein pair
– Recording two stereo channels in a single record groove using the groove walls at 45 degrees to the vertical
– A stereo disc-cutting head
– Using hybrid transformers to mix left/right signals and create sum/difference signals

Blumlein’s stereo experiments began in early 1933, and the first stereo discs were made that same year. Development for cinema use was completed by 1935. His test films, such as "Trains at Hayes Station" and "The Walking & Talking Film," demonstrated his goal of making sound follow actors on screen.

In 1934, Blumlein recorded Mozart’s Jupiter Symphony conducted by Sir Thomas Beecham at Abbey Road Studios using his vertical-lateral technique.

Television development involved many people and companies during the 1920s and 1930s. Blumlein’s work for EMI began in 1933 when his boss, Isaac Shoenberg, assigned him full-time to TV research. His contributions included:
– Resonant flyback scanning (British Patent No. 400976, filed April 1932)
– Using constant-impedance networks in power supplies (Patent No. 421546, filed June 16, 1933)
– Black-level clamping (Patent No. 422914, filed July 11, 1933)
– The slot antenna (Patent No. 515684, filed March 7, 1939)

Blumlein played a key role in creating the waveform structure used in the 405-line Marconi-EMI system, which supported the UK’s BBC Television Service at Alexandra Palace. This was the first scheduled "high definition" (240 lines or better) TV service and later became the CCIR System A.

Blumlein was central to developing the H2S airborne radar system, which helped guide bombs during World War II. After his death in June 1942, many feared the project would fail. However, it succeeded and helped end the war. His role was a secret at the time, and his death was announced briefly to avoid giving Hitler hope.

Blumlein’s invention of the line-type pulse modulator was a major

Death and investigation

On June 7, 1942, Blumlein died in a crash involving a test aircraft called a Handley Page Halifax. The plane was being tested for the Telecommunications Research Establishment (TRE) and was equipped with special equipment called an H2S system. The flight began at RAF Defford. At an altitude of 500 feet (150 meters), the aircraft’s engine caught fire. The fire grew quickly, and the plane lost altitude, rolled upside down, and crashed near Welsh Bicknor in Herefordshire. Two other people, Cecil Oswald Browne and Frank Blythen, also died in the crash.

The Halifax was carrying a secret device called a cavity magnetron, which was part of the H2S test system. Because the device was highly important, a team led by Bernard Lovell recovered it from the crash site the same night.

An RAF investigative board completed its report on the crash on July 1, 1942. The report was shared only with a limited group of people and not made public. Due to wartime secrecy, the news about Blumlein’s death was not announced for three years. The board, led by AIB Chief Inspector Vernon Brown and supported by Rolls-Royce (which made the plane’s Merlin engines), concluded that the crash was caused by an engine fire. The fire started when a nut on the starboard outer engine became loose because an RAF worker had not tightened it properly during an inspection three hours before the crash.

During the flight, the loose nut caused the engine’s valve clearance to increase. This led to the valve head hitting the piston, breaking the valve stem. The broken valve allowed fuel and air to mix inside the engine, which was then ignited by the spark plug. The fire spread rapidly along the engine and wing, causing the starboard wing to break off at about 350 feet (100 meters) altitude. Without the wing, the plane lost control, rolled upside down, and hit the ground at about 150 mph (240 kph).

The board found that the crew and passengers did not escape immediately because the plane was losing altitude, the fire blocked exits, and not enough parachutes were available or worn. Soon after the crash, Prime Minister Winston Churchill ordered that all test flights with civilians or scientists must carry enough parachutes for everyone on board.

The RAF board’s report was ordered to remain secret by Churchill. The cause of the crash was not made public, even to the families of those who died. This led to many false rumors that German sabotage caused the crash, which spread for many years afterward.

Personal life

Alan Blumlein had two sons named Simon Blumlein and David Blumlein.

Outside of his work, Blumlein enjoyed music and tried to learn how to play the piano, but he stopped. He liked horseback riding and sometimes went cub hunting with his father-in-law.

He was interested in many areas of engineering, such as aviation, motor engineering, and railway engineering. He earned a pilot's license and flew Tiger Moth planes with the London Aerodrome Club at Stag Lane Aerodrome. Once, he asked a bus driver if he could drive the bus from Penzance to Land's End. On another occasion, he helped the person who operated the railway signal box with their work at Paddington Station.

Tributes

• Alan Blumlein Way is a road located on the Tektronix campus in Beaverton, Oregon. The road is named after Alan Blumlein, who made important contributions to the field of electronics.

• A meeting room called the Blumlein Room is located at the Institution of Engineering and Technology (IET) headquarters in Savoy Place. The room was renamed after a major renovation in 2015.

• A blue plaque was placed on Alan Blumlein’s former home in Ealing in 1977. The plaque was installed by the Greater London Council to honor his achievements.

• On April 1, 2015, the IEEE presented a milestone plaque to Alan Dower Blumlein for inventing stereo sound. The ceremony took place at Abbey Road Studios and was attended by many experts in audio and recording. The plaque is now displayed on the right side of the front door at Abbey Road Studios.

• In 2017, the Recording Academy honored Alan Dower Blumlein with the Technical Grammy Award. He was recognized for inventing stereo sound and making important technical contributions to the recording industry.