New Book by Bob Cordell: Designing Audio Circuits and Systems

Designing Audio Circuits and Systems will have its 1st Edition published in April 2024, and advanced copies are being sent to reviewers, which includes audioXpress. Bob Cordell, wrote this new book as a comprehensive guide to audio circuits and systems design, beginning with analog audio basics, all the way through to in-depth design techniques for home and professional audio preamps, amplifiers, filters, equalizers, and even headphone amplifiers and DACs.

Linear Integrated Systems, the world class producer of ultra-low-noise JFETS and other small-signal discrete semiconductors, has announced the re-release of its LSK489 discrete component with specialized parameter grading. The LSK489 is one of the world's premier JFETs optimized for use in high-end sensor front-end amplification designs, and the re-release in 2022 introduces improved manufacturing consistency.

Linear Systems announced the re-release of the low-noise, low-cost LS844 series dual JFET with immediate large-scale availability and large-volume pricing. The re-released LS844 is the latest evolution of a classic dual JFET developed and introduced by Linear Systems over 20 years ago. The company has refined the part’s design and fabrication processes to improve its low noise, matching and Common Mode Rejection Ratio qualities while retaining the linearity and other characteristics sought by audio and other circuit designers.

This reference DIY project details of an upgrade construction for the legendary Hafler DH-220 lateral MOSFET power amplifier, which can also be used to upgrade other Hafler models or even inspire new designs. The design is implemented on two PCBs, one as a drop-in replacement for the original Hafler circuit board and another board that consolidates all of the output stage wiring and components within the heatsink and under the main PCB. After the authors detailed the design and performance of the DH-220C upgrade amplifier, in this second part of the article, Bob Cordell and Rick Savas discuss the construction and testing. This article was originally published in audioXpress, August 2021.

This article offers the first serving of an amazing DIY project from amplifier experts Bob Cordell and Rick Savas with an upgrade for the legendary Hafler DH-220 lateral MOSFET power amplifier. The design is implemented on two PCBs, one as a drop-in replacement for the original Hafler circuit board and the other as a new board that consolidates all of the output stage wiring and components within the heatsink and under the main PCB. This article was originally published in audioXpress, July 2021

Linear Audio, the bookzine created in 2010 by Jan Didden, is now available on a USB with The Complete Linear Audio Library. We asked three Linear Audio and audioXpress authors - Gary Galo, Bob Cordell, and Dimitri Danyuk - to review it and share their thoughts. Important to know, the USB drive doesn't contain only the PDFs of published articles. It also ads additional articles by Jan Didden and others, together with materials of historical interest.

Chord Electronics has launched its first ever small desktop integrated amplifier, Anni. Capable of driving both headphones and compact loudspeakers, the small by mighty Anni benefits from the company’s proprietary Ultima circuit topology and is perfectly positioned to exploit the full potential of today’s high-performance headphones, desktop monitors and high-resolution audio sources. The Anni forms part of Chord's Qutest range of compact products and pairs perfectly with the Qutest standalone DAC and Huei phono stage.

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 article describes the design and performance of a high-quality DC-coupled all-JFET amplifier. The circuit was inspired by John Curl and Erno Borbely designs and was built with readily available junction-gate field-effect transistor (JFETs) from Linear Systems. The input stage is the the complementary JFET differential pair, the second stage is symmetrical differential amplifier with two pairs of opposite polarity JFETs, and the output stage is a complementary source follower. The amplifier can drive loads up to 150Ω. This article was originally published in audioXpress, October 2017.