audioXpress August 2021 Focus on Acoustics Issue Now Available

The August 2021 edition of audioXpress is now available in print and online. Read our Acoustical Solutions Round-Up 2021 and enjoy the DIY perspectives from Ethan Winer and Thomas Perazella on dealing with room measurements and treatments. David Logvin reviews Audio Precision's APx517B Acoustic Audio Analyzer, while Richard Honeycutt reflects on acoustic challenges for online and in-person meetings. And we conclude the DH-220C MOSFET Power Amplifier article by Bob Cordell and Rick Savas, and the VSCS Amplifier project in this edition.

One of the strongest issues ever in terms of audio electronics and market insights, audioXpress July 2021 is now available. This edition includes a complete overview of Audio Amplifier Technology and Design and its many application segments. Start with a review of the NAD Electronics M33 Masters streaming amplifier, followed by a great new upgrade design for the legendary Hafler DH-220 lateral MOSFET power amplifier, and then dive into a new hybrid voltage source and current source amplifier design for loudspeakers.

This project is based on a previous audioXpress article: “A Solid-State Single-Ended Power Amp” by Ed Simon, published in the April 2006 issue. Ron Tipton was deeply impressed with this amplifier project which used only five transistors per channel, two of them being current sources. This article was originally published in the old audioXpress website as a PDF, but was never reposted. Now we make available online with updated references and links.

Stuart Yaniger reviews a complete series of professional-grade measurement microphones from PCB Piezotronics, specifically, the 378A04 free-field microphone, the 378B02 free-field microphone, the 378A21 diffuse-field microphone, and the 130E20 array microphone. This article was originally published in audioXpress, December 2016.

In this simple amplifier project, Ed Simon describes a Class-A amplifier design that mainly intends to reproduce music with reinforced emotional expression. That's what you normally get with a quality design, but to achieve it, the author shares the complete concept, power requirements, circuit topology, construction and testing of this single-ended amp... in a solid-state design. This article was originally published in audioXpress, April 2006.

Since its publication in 2010, “Current-Driving of Loudspeakers" by Esa Meriläinen, was received with both enthusiasm and skepticism. Effectively, Meriläinen anticipated the criticism when writing in his book preface: “The subtitle of the book may at first sound too much promising or inflated, which it, however, is not at all; for as will show up especially in chapter 4, the issue is indeed about a fundamental fallacy in sound reproduction technology.” In this article, published originally in Voice Coil, July 2010, Joseph DeMarinis not only reviews the book but also runs tests of the theory.

In this fascinating article, published in audioXpress, October 2004, Nelson Pass investigates loudspeaker performance when driven by a current source amp. This extensive research shows what Pass and Kent English found with a variety of full-range sensitive loudspeaker drivers when they drove them with an active current source and played with parallel networks to shape the response to their liking.

In this article published originally by audioXpress in March 2005, Nelson Pass offers a series of tips about designing filter networks for both voltage and current sources. Nelson Pass provides filter examples that can be used equally well with a voltage or current source.