JFETs: The New Frontier, Part 1

The basic circuits on which Erno Borbely based most of his projects are described in “JFETs: The New Frontiers, Part I and II,” published in Audio Electronics AE 5/99 and 6/99. Referring to these articles frequently, the author admits, these were the “building blocks” on which many - if not all - of his amplifiers are based. This article is the first part, as originally published in Audio Electronics, Vol. 5 1999.

Following its first presentation at CES 2015, Pass Labs has now confirmed availability for its highly anticipated new headphone amplifier. The HPA-1 is able to drive headphones presenting loads from 15 to 600 Ohms. It features a custom shielded toroidal power transformer feeding a discreet low noise regulated power supply, J-Fet input stages and Class A-biased direct-coupled MOSFET output stages.

What can you do to ensure the best possible sound from your system? According to Nelson Pass, the “sweet spot” concept is generally regarded as “that happy balance of conditions that elicits the best possible sound,” including the interiors of the components themselves. This article was originally published by audioXpress, January 2010.

Discrete, logic and analog semiconductor specialist Diodes has introduced a raft of new ICs for consumer electronics and networks, together with new voltage converters and regulators targeting a range of interesting applications for the audio industry. The new AZV5001 headset detection IC is particularly interesting.

Over the years, some of the best Nelson Pass projects have been featured by Audio Amateur and audioXpress magazines. The A40 power amp article was published in The Audio Amateur, 4/78, and the A75 power amplifier appears in The Audio Amateur 4/92 and 1/93. His other works are posted at passdiy.com. Originally published by audioXpress on May 2010.

With a little know-how and some basic parts, you can design a hybrid amplifier in fairly short order. This project combines the best attributes of both tube and transistor technologies.