The meeting of the LRS on 25th January 2017 was a talk on "How Theo Williamson's Amplifier Changed the Sound of Music" which was given by Prof Joe McGeough (above), a former Professor of Mechanical Engineering at the University of Edinburgh, and who knew Williamson in his later years..

The Williamson amplifier refers to a type of valve audio amplifier whose circuit design used the same principles as a design published in Wireless World in 1947 by Theo Williamson (1923-92) of Edinburgh. He proposed the standard which became generally accepted as the target figure for high-quality audio power amplifiers - for less than 0.1% total harmonic distortion at full rated power output.

Theo Williamson photo courtesy The Scotsman.  See link to article at bottom of report.

The amplifier was one of many achievements by Williamson who failed to gain a degree at Edinburgh University by his inability to pass his Maths-1 exam after four attempts!  Joe's talk was a fascinating biography of Theo Williamson and his many achievements, leading to the award of a Fellowship of the Royal Society in 1968.


Prof Joe McGeough was introduced by Dr Brian Flynn GM8BJF, with whom he has written a number of scientific papers.


 These Powerpoint slides are reproduced with Joe's permission.


 The Town House in Gilmore Place where Theo was born and raised is now a B&B guesthouse.


Plaque to Theo Williamson beside the front door of the Town House B&B at 65 Gilmore Place, Edinburgh.


After attending James Gillespie's Primary School, Theo completed his schooling at George Heriot's.

His prize for constructing a radio-controlled boat (in the 1930s) was an indication of his future potential.


Theo then went to study Engineering at the University of Edinburgh, but did not graduate.



Theo no doubt drew comfort that a number of famous Scots failed to complete their degrees!


Theo was then turned down for a position in the scientific civil service by no less than C.P. Snow, later Lord Snow.


So Theo got a job with the M.O. Valve Company in London, in the Valve Testing Department. Without a degree, this was the best he could hope for - one of the most boring jobs imaginable! However, after he had tested his allocated number of valves in a day, he was free to work on his own ideas, which included sound amplification.


Theo designed and built what became recognised as the first High Fidelity (Hi-Fi) audio amplifier. It employed push-pull circuitry in both the driver- and output stages and set the criterion of no greater than 0.1% total harmonic distortion at full power output, which remains the standard today. 


(Photo courtesy of the Science Museum, London).


Theo did not patent his design and thus received no royalties from it after its great success.


After the war, Theo returned to Edinburgh to work for the famous electronics firm of Ferranti, heavily involved in government / defence contracts.



It was at this time that Theo started to employ computers to improve the quality, consistency and especially volume of manufacture of radar components in the early years of the Cold War.




After 14 years at Ferranti's, Theo was offered a job in London by Molin's who made tobacco equipment.

At a salary higher than that of the Prime Minister, he could hardly refuse!


Theo applied his computer-control of manufacturing here with great success.


These systems are now universally applied in industry.



Graph illustrating the predicted fall in the UK's trade balance unless modern manufacturing methods such as Theo's were introduced.











After Wills bought Molins and stopped the research work, Theo had to leave.







Finally Theo was awarded a degree by the University of Edinburgh, many years after having leave because of his failure to pass his Maths-1 exam!


Theo's legacy lives on at George Heriot's School.


 LRS President presented Joe with a token of our appreciation after his talk.

Click for Scotsman Article about Theo Williamson.