You Can DIY! eDD - A Direct-Drive Amplifier for Electrostatic Speakers

This article details a lifetime project from audioXpress' technical editor Jan Didden. After a successful restoration project of a pair of precious ESL-63 Quad electrostatic speakers, he opted to design and build the eDD, a well-performing high voltage amplifier to directly drive electrostatic speakers. This challenging but successful DIY project with a design goal of 1500V RMS at 20mA RMS over the full audio band, took a while to complete but was a success. This article shares every step of the construction.

Now that headphones and earphones are adding situational awareness, hearing protection and hearing enhancement features, HEAD acoustics created new test methods to evaluate these functions, faithfully simulating environments that a consumer might typically encounter when using products with these features. As an experienced reviewer in this category, Brent Butterworth was invited to visit HEAD acoustics' US headquarters in Brighton, MI, to learn about all the solutions the company has developed for this purpose, based on measurement techniques outlined in ETSI standards.

The AX5689 is an eight-channel audio amplifier controller IC with digital inputs and CMOS level PWM outputs, enabling high-order digital control loops with post-filter feedback. This article, originally published in audioXpress, December 2023, reviews the Axign and GaN Systems Class-D audio amplifier reference design board, intended to demonstrate the benefits of Axign's digital controllers and its unique approach.

This article describes bass and treble tone control circuits where the frequency at which control begins in each band is variable over a 16 to 1 range, making it much more useful for correcting speaker deficiencies or room anomalies. Something that very few manufacturers have offered. This article was originally published in audioXpress, December 2023.

This is the last issue of Voice Coil for 2023, which includes a combination of valuable industry resources and expert knowledge for loudspeaker engineers. Mike Klasco and Nora Wong (Menlo Scientific) have compiled an updated directory of Engineering Simulation Software and Test & Measurement Hardware Vendors. And in Test Bench, Vance Dickason characterizes the latest PTT8.0X04-NAB-02 8" aluminum cone woofer from Purifi Audio.

audioXpress December 2023 includes a market overview of multiroom audio, Brent Butterworth writes about new ways to measure ANC earbuds, and Stuart Yaniger measured the new Axign and GaN Systems Class-D audio amplifier board. Richard Honeycutt writes about tubes, BJTs, JFETs, MOSFETs, and ICs, and Dimitri Danyuk, discusses JFETs in audio circuits. Douglas Self explains how to optimize variable-frequency tone controls, and Jan Didden shares his eDD direct-drive amplifier project.