Testing, Measuring, and Smart Audio Solutions in audioXpress December 2020

November 11 2020, 15:10
Ending the year with great content, as we do 12 times per year, audioXpress December 2020 is now available in print and online. In this edition, we pay tribute to Jeff Bagby, explore the QuantAsylum QA401 audio analyzer combined with the new QA451 programmable load, and explain the process of measuring wireless audio products using multi-tone testing. Plus, Brewster LaMacchia expands on A2B designs, Gary Galo details how to improve low-output moving-coil cartridges with his Jensen-based step-up transformer, and Mike Harkins reviews the versatile Puffin Phono DSP by Parks Audio. And much more, now available!

It might be the last audioXpress issue of 2020 - a difficult year for most of us, no doubt - but that left us even more determined to end the year with a great edition, with varied, valuable content. We think we did just that, as anyone quickly browsing through the cover highlights will quickly realize. But the real stuff is inside.

Starting fittingly with a tribute to the amazing Jeff Bagby, who positively inspired so many of us and sadly passed away this year. The entire audio community realized a deep sense of loss and sadness for the disappearance of one of its friendliest voices, one of the most enthusiastic speaker builders and a prolific contributor to the global DIY audio community. To highlight the significance of Jeff Bagby’s contributions, we asked one of his lifelong friends, Ben Shaffer, to look back on his work and help us preserve his memory.

On our cover for December 2020, many of our readers will instantly recognize the familiar look of the increasingly popular QuantAsylum QA401 audio analyzer. What many readers might not recognize is the second module, the completely new QA451 programmable load, so new that audioXpress tested a pre-production version. Effectively, for this edition David Logvin offers is valuable perspective of this modular solution for audio measurements from QuantAsylum. Putting the systems to use in actual tests, Logvin explains the software features, and fully explores these affordable hardware solutions, offering up to a 192kHz sample rate, differential inputs and outputs, full-isolation from the USB-connected host, and programmable electronic loads permitting rapid power amp testing up to 200W. 

Another of our cover highlights focuses on wireless audio. In "Mastering Wireless Multi-Tone Testing," Andrew Taylor (Klippel GmbH) explains the issues resulting from measuring a wireless audio connection and how wireless multi-tone testing can help us to overcome those obstacles. The article is written from a Practical Test & Measurement perspective, particularly focused on the needs of manufacturers and designers of modern wireless audio devices and offers valuable insights on multi-tone testing.

This month, we also bring two great articles on phono circuits. First, audioXpress expert Gary Galo details how to improve the vinyl enthusiasts' favorite experience with low-output moving-coils, by building a passive MC step-up transformer. After reviewing multiple products using Jensen transformers, Galo decided to build his own step-up device and shares his experience in this project article.

In the second article on the topic, Mike Harkins reviews the versatile Puffin Phono DSP by Parks Audio. For those of you who are not familiar with Parks Audio, this company was founded by Shannon Parks, who has also contributed fantastic articles published by audioXpress. After experimenting with several other products, Parks Audio has achieved notoriety for its phono stage Puffin, which adds a programmable DSP and is able to be updated and improved constantly with simple firmware updates. A new approach that truly takes the concept of a phono stage to a different level.

But there's a lot more to read. In his regular Sound Control column, Richard Honeycutt writes about the "Acoustical Design of a Multi-Purpose Room." The article explores how to use a careful acoustical design to provide excellent acoustics for contemporary music concerts, speeches, and social events, even in large, difficult spaces. In this case, Honeycutt shares his real experience when asked to consult on the acoustical design for renovation of a church multi-purpose room that presented some interesting challenges.

In his Audio Scope column, Michael Steffes continues to explore audio DAC output designs implementing a differential transimpedance first stage into a differential to single-ended stage, providing an active filter in that second stage. This month the experienced audio IC designer explores some existing circuit examples, and proposes some simple linearity improvements for these designs.

In his Hollow-State Electronics column, Richard Honeycutt returns with more historical perspectives of classic tube circuit designs, exploring hollow-State recording mixers. He discusses the beginnings of audio mixers and shares some tips for DIYers who might want to design their own, including by assembling one from the many 500-series preamps and a home-brew summing amp.

Finally, audioXpress continues Brewster LaMacchia's article series on Automotive Audio Bus (A2B) (not just for automotive). After an introduction to the properties of this locally networked audio transport that has very low and deterministic latency and comparisons with existing digital audio interfaces, the series continues to look further into A2B system design, bus topology, and phantom power features. For this December 2020 edition, LaMacchia looks more closely at A2B data transport and how to interface between peripherals and the A2B bus using parts made by Analog Devices.

This is another example of audioXpress' content, published 12 times per year and available in print and online. Subscribing to the digital online version allows immediate access at: www.audioxpress.com/page/audioXpress-Subscription-Services.html

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