You Can DIY! Designing a Powerful Speech Compressor

This project describes a dynamic compressor circuit working in reverse. Instead of limiting the maximum volume level of an audio signal, it leaves loud parts alone and instead raises the volume when it’s too soft. The project uses a famous VCA circuit designed by David Blackmer of dbx fame, developed in the 1960s, whose patent expired long ago. The resulting original design is useful for transcribing conference meetings, court reporting, or any other situation where the volume level of recorded speech can vary by a large amount.

audioXpress July 2024 is all about Audio Amplifiers. Jan Didden visits ICEpower. Ward Maas interviews Jan-Willem Winters from Hypex. Oliver Masciarotte reviews the WiiM Amp. Thomas Lund explains why Loudness Normalization is so important. Richard Honeycutt explores the new Orange Valve Tester MKII. Brewster LaMacchia explains all that has evolved in Ten Years and Three Generations of A2B. Ethan Winer details how to build a truly unique Speech Compressor. And so much more...

Since the dawn of the digital era decades ago, the timing error known as "jitter" in A/D/A converters has been accused of harming audio fidelity. Some people claim that jitter adds audible distortion and noise, affects bass fullness, and even harms stereo imaging width and depth. This article explains what jitter is, what causes it, and even lets you hear jitter in controlled amounts so you can decide for yourself how damaging it really is. Originally published in audioXpress, January 2024.

In audioXpress January 2024, Martin Turesson explains how Thin-ply Carbon Diaphragm (TPCD) technology can be applied also to headphones, and Claus Futtrup writes about Loudspeaker Bass Reflex Alignments. Paul Marchese discusses Composite Amplifiers, Roger Tall explains how a research effort allowed ClarityCap to understand the impact of resonances in capacitors. Our own Jan Didden interviews Robert Munnig Schmidt, while audio expert Ethan Winer explores audible consequences of jitter in digital audio conversion.

This original circuit effectively removes the low-frequency impulses caused by air blasts from a person speaking or singing into a microphone, as well as "plosives." This analog circuit removes these irritating sounds in real time, directly at the source by applying a 24-stage all-pass filter to delay only the lower frequencies of the main audio stream. This original circuit for non-commercial use is available for licensing for commercial manufacture. This article was originally published in audioXpress, October 2023.

In the October 2023 issue of audioXpress, Jan Didden visits Dutch & Dutch, Reinhold Lutz shares a practical way to measure loudspeakers in any room with his AudioChiemgau Mode-Compensator, which is tested by Rens Tellers. We have two DIY open baffle projects from Perry Marshall and Charlie Laub, Richard Honeycutt writes about the Western Electric 91E, and Ethan Winer shares his Popping P Filter circuit. In the Sound Control column, Honeycutt explores Passive Variable Acoustics, and Chuck Hansen concludes his article series on Power Transformers. audioXpress October 2023 is now available in print, digital, and online.

The first article from audio expert Ethan Winer about Modern PCB Design Practices, gave a general overview of board design using surface-mounted devices (SMDs). The article examines current practices and methods for designing four-layer printed circuit boards using surface mounted components (SMDs), and this second part explains specific strategies and related issues to deal with the design and production of great quality PCBs. This article was originally published in audioXpress, March 2023.

In this two-part series, Ethan Winer examines current practices and methods for designing four-layer printed circuit boards using surface-mounted components (SMDs). A great article for our DIY readers and many developers who often are faced with the need to build and test their projects on a properly designed, prototype printed circuit board. Part 1 presents an overview of the process, while Part 2 he will explain specific strategies. Many related issues will be described along the way.

audioXpress March 2023 offers an overview of the latest solutions and trends in audio measurement. Stuart Yaniger reviews the new Echo AIO modular audio test system, Philipp P. Klose writes about measurements in automotive audio environments, and Steve Temme shares his knowledge on audio testing in the production line. René Christensen explores Lumped Element Modeling of Transducers, Chuck Hansen expands the topic of power transformer losses, and Ethan Winer concludes his two-part article about Modern PCB Design Practices.

audioXpress February 2023 focuses on the small devices in the increasingly larger market of MEMS Microphones and Voice Pickup Sensors. The Market Update on this topic is complemented by Erica Yorga's article on the principles of Nureva's Unified Coverage Map. Ethan Winer offers the first of a primer on modern PC board design, there's a review of the Arylic Audio Up2Stream Amp V4 board, an inside story on how Crestron adopted AES67, and a High-Performance Tube Hybrid Preamp DIY project.