http://www.stereophile.com/content/h...tching-amp-thxWhen I gave my Richard Heyser Memorial Lecture at last October's AES Convention, THX's Laurie Fincham was sitting in the audience. Afterwards, Laurie whetted my appetite for what the company would be presenting at CES: a patented non-switching power amplifier topology that would be as efficient as a class-D amplifier but without the side-effects that afflict such designs, high levels of radiated RF, for example. In the photo, Laurie is pointing to the power supply of the amplifier. DC is fed to two oscillators running at 25kHz, one generating a sinewave, the other a cosinewave, ie 90° out of phase with the sinewave. Each wave feeds a transconductance amplifier in the primary pf a tiny transformer; the output of each secondary is rectified and summed to produce a high DC voltage which is then used to power the amplifier circuit. There are no storage capacitors in the circuit—it looks as if almost all the energy entering the supply is available as the final DC voltage! The new topology was developed by Fincham, Owen Jones (the twin brother of TAD's Andrew Jones) and Andrew Mason.
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