Fresh From the Bench: Purifi 1ET9040BA Balanced Class-D Amplifier Module

The Purifi 1ET9040BA balanced Class-D amplifier module, a Bridge-tied-load (BTL) output stage, is the second product in the company's Eigentakt range. Following a conversation with members of Purifi about the amplifier's audio performance being hard to measure even with the best available test equipment, Jan Didden, in collaboration with Rens Tellers, took up the challenge, with invaluable support from Audio Precision's parent corporation Axiometrix.

The QuantAsylum QA403, the 4th generation audio analyzer from the company founded by Matt Taylor in 2012, has a lot to offer. In particular when a user gets tips and guidance from someone like Bob Cordell, no less. The QuantAsylum QA403 Analyzer was the result of a complete redesign imposed by the silicon shortages and supply chain disruptions, pre- and post-pandemic. It appears that the efforts made were well worth it. Jan Didden shares his impressions.

We looked at the popular articles of 2024 in audioXpress.com (including selected articles from audioXpress and Voice Coil magazines), and we created this Top 11 list of news stories and online articles. As the number of visitors and pageviews registered by audioXpress.com continues to break records every year, visitors from all over the world returned more often to read the more than 10,400 stories available. Which of the topics and stories published online in 2024 were the most popular? Here are the results!

Designing Audio Circuits and Systems is a surprising effort by the author and one that deserves careful exploration. A true compendium of lessons in audio that reflects Bob Cordell’s long-standing track record of designing audio equipment as well as advanced test equipment. The vast content contained in this book makes it an essential reference for anyone designing audio circuits, including excellent “hands-on” material for anyone starting to experiment in audio electronics.

Or why not all grounds are created equal. How to mitigate grounding issues in audio equipment, understanding resistance, inductance, and capacitance of ground wiring, and voltage differences between points. Also, how not add to the construction complexity.

Ask audio industry insiders and audiophiles alike about Joachim Gerhard, and chances are that they mention the many high performance speakers he designed over the years. But he also has a great track record designing phono preamps and this interview explores that aspect of Joachim’s career. In this second part of the interview, Jan Didden explores Gerhard's design ideas and goes into details on his Discrete INA design, a discrete input stage instrumentation amplifier topology.

Ask audio industry insiders and audiophiles alike about Joachim Gerhard, and chances are that they mention the many high performance speakers he designed over the years, initially for Audio Physic, currently for Suesskind Audio. But Gerhard also has a great track record designing phono preamps. This interview explores that aspect of Joachim’s career. In the first part of this interview Joachim discusses the design considerations and circuit topologies for low noise phono stages, culminating in his very low noise and Flexible Phono Stage (FPS) design. This article was originally published in audioXpress, September 2024.

This article explores the significance of the Rds(on) specification of a MOSFET in a linear voltage amplifier and implications on Thermal Design - dissipation, thermal resistances, and heatsinking. It may be of interest to put this in perspective and highlight the connection between these subjects.

Europe’s Nordic countries have long been the birthplace for high-quality and innovative audio products, particularly excelling at speakers and amplifiers. Located near Copenhagen, ICEpower has traditionally been known as a purveyor of high-performance Class-D amplifiers and associated switch-mode power supplies. The company continues to provide innovative Class-D solutions today, but its scope is now much broader than that, as this report discloses.

Series voltage regulators are a great way to provide almost-noise free and rock-stable DC to your audio circuits. But the load current often has distorted signal components that can generate a ‘dirty ground’ across the supply ground wires and tracks. This can introduce distortion components in other circuit sections using this ground. With shunt regulators we can keep the dirty ground localized and largely avoid the problem. Technical Editor Jan Didden explains.