Arch Nemesis — Nelson Pass / 2010

A poster of Einstein once said, “Things should be made a simple as possible, but no simpler”. This can apply to audio amplifiers, but if they are evaluated subjectively, the simplicity thing can get a little of of hand. Of itself, minimalism exerts a strong aesthetic attraction, and there is a reasonable belief that fewer components in the signal path allows more information to get through with less coloration. If like me you are interested in understanding of how we hear distortions with our brains (instead of our meters), you might appreciate that simple circuits help isolate these phenomena. I… More...

Zen I/V Converter — Nelson Pass / 2010

Thirteen years ago Pass Labs launched the D1, a dedicated Digital to Analog converter for high end audio. It was based on balanced PCM63 DAC chips with a current source output, which requires a separate current-to-voltage converter (known as an I/V) to turn its output into the voltage to drive other line level audio equipment. We didn't care much for the op-amp based solutions seen in the manufacturer's application notes and decided to approach this part of the circuit much differently. The PCM63, like other current output DACs, favors driving a very low impedance, preferably ground. You can easily create… More...