You Can DIY! The DH-220C MOSFET Power Amplifier - Part 1 The Circuit

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

This Test Bench characterizes the Beyma 12LEX1300Nd 12" driver from Beyma's new LEX Series. This latest design features a FEA-optimized neodymium magnet structure and 4" voice coil, and is targeted at two- and three-way PA speakers, or band-pass subwoofer designs. The entire woofer is optimized with a substantial set of features for very high-performance, including the company's unique Maltcross forced convention cooling system. This article was originally published in Voice Coil, July 2021.

The Purifi Audio PTT6.5X04-NFA-01 midbass transducer is an over-achiever, and to help understand why, Dickason talks with Lars Risbo about the research and thought process that lead to many of the features found in this woofer. Including the unique cone assembly that consists of a mildly curvilinear paper cone made with a proprietary fiber mix, a 3.13” concave dust cap, and a V-shaped edge reinforcing ring, the NBR surround, and what Dickason calls "probably the most unique surround in the history of Voice Coil’s Test Bench. This article was published in Voice Coil July 2021.

After reviewing the compact but mighty M10 Masters Series streaming amplifier from NAD Electronics, Stuart Yaniger simply had to try the new flagship NAD M33 Masters streaming DAC amplifier. This was the first mainstream product to implement the Purifi Audio Eigentakt (self-clocking) amplifier modules, but there is a whole lot more to make it a very complete package for a musical life. The article, published in audioXpress, July 2021, reviews the experience and performance measurements.

More than five years in development and after multiple iterations, Australian startup Nuheara achieved its goal with the Nuheara IQbuds2 MAX, a bridge toward truly smart hearables. This advanced design uses digital technology to bring hearing aid functionality into true wireless earbuds. audioXpress asked Brent Butterworth to try them and share his experience and evaluation. This article was originally published in audioXpress, July 2021.

Voice Coil July 2021 is now available and full of valuable articles. Starting with Mike Klasco's insights on glue joints and attachment techniques used in speaker design. Followed by an updated and comprehensive directory of manufacturers and suppliers of adhesives, coatings, and treatments for the speaker industry. James Croft reviews the recent Bidirectional Speaker patent awarded to Resonado Labs, and Vance Dickason places the totally unique Purifi PTT6.5X04-NFA-01 midbass driver on Test Bench, followed by Beyma's 12LEX1300Nd 12” woofer with its unique Maltcross cooling system. Now available in print and online!

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.