The JLH Gateway-- A Golden Jubilee Tribute

The Millennial March-past The simple, yet novel circuitry of the JLH did indeed trigger the creativity of DIYers and 'circuit honchos'. Quite a few among them, who were respected designers in their own right, came out with namesake amplifier designs, and that was how we got to see the PLH, DLH etc series of amplifiers joining the Class-A cavalcade. Guess what! The PLH amplifier which came out in 2005, was by the "grand-daddy of audio design" Mr Nelson Pass. As Mr Pass so disarmingly puts it " ... I stripped down the JLH to the simpler MOSFET topology ... and (ahem!) added my initial to the name!"           But it is heartening to see how a great designer like Mr Pass pays his respects to another genius designer like JLH. How Pass analyzes the JLH circuit is a good lesson for enthusiasts, and the entire article is recommended (repeated) reading, if you ask me. The reader is enjoined to visit the Passdiy site for a detailed post (as is typical of Mr Pass...

A  Class-A  Cavalcade ... and More!           It would be interesting to take a look at the Class-A amplifier scene around the time JLH was thinking of an amplifier to replace his trusty Williamson amp. Of course, a few solid-state Class-A designs were there, but none had achieved cult status, so to speak. Contemporaries of JLH included well known and respected designers like Nelson-Jones, Dinsdale, I.M. Shaw, Arthur Bailey, J. E. Sugden, Stan Curtis and others.           It was in the mid-sixties that the young engineer James Sugden founded his company, coming out with the famous A21 amplifier, famed to be the first production Class-A amplifier. But the company website today claims that it was the Si402 model (not a very popular model, nor produced in large numbers, apparently) that has the honour to claim that title.  Sugden Amplifiers - Old and New           Whatever, Mr Sugden p...

Building the JLH Classic --  Moss the Torch Bearer Sic transit gloria mundi ... Thus passes the glory of the world. .. For JLH enthusiasts and for those who knew him and his work, the year 2004 was indeed a sad one -- they lost the guiding spirit that JLH was to all of them. The Electronics World (formerly Wireless World) magazine declared the June, 2004, issue as a JLH Memorial Issue , and in his honour reprinted  the entire article of the JLH Classic amplifier  from the April, 1969, Wireless World, a very rare tribute paid to any author. Cover of Electronics World (UK) June, 2004 Contents Page - EW June 2004 JLH had never chosen to be in the limelight, and his admirers were happy to see a rare current photograph of the Master in the Obituary / Tributes column published in the EW June, 2004, issue. But today, looking back, it is heartening to note that the legacy and glory of JLH lives on, thanks to the efforts of a few dedicated souls like Geoff Moss, and the continuin...

Building the JLH Classic --  Gilding the Lily JLH Strikes again! The avid designer and hobbyist that he was, JLH did not rest on his laurels after the unprecedented interest and dedicated following that his class-A amplifier design generated. As we saw earlier, JLH was not casually designing something for an audience; rather, his primary aim was to derive musical pleasure from his designs, which he built with his own hands. Surely we must give him credit for being updated with the contemporary happenings in the audio electronics field on both sides of the Atlantic, with a score of other designs emerging, shooting for improved performance, power etc.  The Americans apparently were going in another direction, mostly chasing high powered amplifiers and huge speakers. This admirably fell in with their larger homes/rooms and their taste for 'big band' sound. A cursory glance at the contemporary technical journals will vouch for the veracity of this observation. Particular mention m...

Building the JLH Classic --  Milestones of the Era Today, as we look back and focus our sights on the JLH Classic, it would be educative to broadly, though briefly, survey the audio electronics landscape of the era. Unarguably that alone would reveal the correct perspective regarding the genius of JLH and his timeless design, rather than label his class-A amplifier as 'one of the typical designs' of the era. Happily the JLH Class-A was not just another 'typical design' of the period -- it had nothing that went before it, and on which it was based. Not only that, the design had many unique features despite appearing to be quite basic. Suffice to say, its apparent simplicity hid within itself many subtleties of design not easily revealed to the casual investigator or circuit hacker. No wonder it has defied the efforts of many talented designers to 'pin it down' and analyze it threadbare.  GOM and old timer Nigel Pearson has put it wonderfully thus: "It makes ...