post #1 of 1
Thread Starter 

JLH also pioneered the use of Star Earthing in SS audio design[yes tube design had been using it for along time]

              John went into great detail in electronic mags about star earthing especially in his early 80s 80W RMS -Mos-fet output HI-Fi amps

              Up to that time it was a case of [in most amps] of just terminating the earth at the input in SS amps.

              John isolated the inputs and took them to the volume controls-his amps having a high sensitivity of 150MV-into 150Kohms for FULL output-A lot harder to achieve low distortion  than on a low sensitivity amp.

              One reason he could hear the difference in capacitors.

              from the volume control earth he took it to the center tap of the mains transformer.

              All input earths were isolated from the output earths by a small value resistor and also taken back to the star earth.

             John was criticized by RF design engineers till it was pointed out to them the different physical properties of low frequency in relation to high frequency. But his methods allowed for a very low amount of mains noise/ripple.So his amps sounded clearer.

             In a letter  to  EW  I wrote that I took Johns principles of reducing noise via earth returns to the ultimate conclusion.        I converted  Johns 80W amp  to 15 W -RMS-class A at 1.5 amps in doing so I made them mono-block with separate outboard PUs .

               These I made star-earthing with the PUs having "floating" earths back to the amps .

               I positioned the star earth directly below each PCB and ran an earth return from EVERY component that required an earth return- looked bad? yes BUT this gave me so great a stability  I only needed a very small value for the compensation cap.It was commented at the time as-by one readers letter-We   will need to take more care of how earths are run in SS amps-Remember this was a long time ago for something you take for granted now.

             John also made a point of using -MOS-FETS in his PAmps criticized by some as -BJTs are more linear but mosfets have a higher FT than  BJTs so a lot more NEGATIVE FEEDBACK can be applied to make them more linear. They also "sound better"subjectively 

                          This is another area John pioneered

                          I hope he is given credit for this in the future.