audioXpress January 2025. Innovations in Audio. Product Development. The Best in DIY Audio

In this issue we write about some of the most innovative Drivers and Transducers from the past two years. Read about dual-driver true wireless earbuds, and how to assess listening effort inside vehicles. Douglas Self shares his latest findings on Modern Op-Amp Distortion Tests, and René Christensen explores the analytical framework that sustains great simulation techniques. Reviews of the APL Virtuoso v2 Binaural Renderer, and the Purifi 1ET9040BA amplifier module.

Whether it is power amplifiers, vinyl reproduction preamplifiers, active crossover filters or, as in this case, small-signal circuits for a very wide range of applications, Douglas Self is one of those authors who consistently has produced reference works about technical audio. You may think that as a fourth edition, it would just be a refinement on the three editions that went before it but Self always adds new material and new insights to make it worthwhile to get this new book.

The March 2024 issue of audioXpress includes an overview of the latest Audio Test and Measurement solutions, a review of the Listen SoundCheck 21 and AmpConnect 621 test suite, and a tribute to 20 years of Room EQ Wizard (REW). Learn how to build a True-RMS Voltmeter and what's behind the myth of Second Harmonic Distortion. Learn how motion feedback technologies can be applied to speakers, and how our hearing process affects our audio listening experiences, and much more. Dive in now!

Douglas Self shares real experiments when selecting electrolytic capacitors to achieve the lowest distortion. An experiment inspired by his recent audioXpress article, "Optimizing Variable-Frequency Tone Controls," available online. This short piece is an interesting closer examination on the subject for audio circuit designers. Originally published in The Audio Voice newsletter, #453, January 11, 2024.

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.

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.

Another great research article from Ethan Winer, where he designed a simple device that measures capacitor distortion using a USB sound card and free software to try and determine the importance of high-quality capacitors in the signal path. This article details the results of his tests with different capacitor types. This article was originally published in audioXpress, May 2020.

In this edition, audioXpress pays tribute to one of its most esteemed and prolific writers, Ron Tipton (1936–2018). In our cover feature, Scott Dorsey details his fascinating visit to the Library of Congress National Audio-Visual Conservation Center. Tom Perazella concludes the construction of his flagship Egg Speakers, Andy Lewis explains more about Back EMF, Peter Lehmann shares his time-alignment design for a two-way speaker, and Ethan Winer shares his experience with the affordable LabNation SmartScope USB oscilloscope. And that's just the start of another great edition, now available in print and online.

Another edition of audioXpress is now available, and this is another one of those issues you don't want to miss. On our cover, we call your attention to Tom Perazella's amazing Egg Speakers, a project which we continue to detail this month. Next, Stuart Yaniger reviews the latest Phantom Power Microphones from PCB Piezotronics, we discuss advanced test methods for improving Active Noise Cancellation headphone performance, and we interview Michael Goodman, CEntrance Founder and CEO. And there's more speaker projects, and great audio theory articles. Download it now or subscribe!

Peter Delos details how to add tone controls to a three-channel tube-based guitar preamplifier. The circuit is a versatile building block anyone can use for his or her own preamplifier applications. The project is implemented with three 12AX7 gain stages. The tone control at the final output is a standard bass, mid, treble control circuit found in many guitar amplifiers. This article was originally published in audioxpress, October 2014