audioXpress Magazine      December 2020

  audioXpress remains the authority on audio and reproduced sound by connecting manufacturers and distributors with developers, buyers and consultants around the globe! It's readers are the audio product designers, consultants, integrators, DIY enthusiasts, opinion leaders and your best customers. All of them agree that the coverage of trending topics, unique in the audio industry, make audioXpress a must read.

Every month, audioXpress combines the best educational articles on topic such audio electronics, speaker and headphone design, amplifiers (from tube to Class D), acoustics, practical test and measurement, audio engineering praxis, and standards. audioXpress provides inside stories on new audio developments, on R&D Stories, the most complete objective reviews of innovative products and software, and selects some of the best DIY audio projects from worldwide experts.

Comment
4 From The Editor's Desk
For Future Memory
It seems like leaving 2020 behind is the only good thing we can look for.
Editorial By J. Martins

8 Remembering Jeff Bagby
By Ben Shaffer
Jeffery Allen Bagby passed away in March of this
year. On that day, the audio community lost one of
its most prolific contributors to the global DIY audio
community. One of Jeff Bagby's lifelong friends, Ben
Shaffer, reflects on his work.

26 QuantAsylum QA401 / QA451
Redefining the Compact and Modular Audio Measurement System
By David Logvin
David Logvin explores a valuable solution for audio
measurements. The QuantAsylum QA401 audio
analyzer is a complete standalone system of hardware
and software that keeps evolving and growing in
popularity, now complemented with the completely
new QuantAsylum QA451 programmable load — so
new that Logvin tested and even helped debug a pre-production
version.

34 Mastering Wireless Multi-Tone Testing
By Andrew Taylor
This article explains the issues resulting from
measuring a wireless audio connection and how
wireless multi-tone testing can help us to overcome
those obstacles.

38 The Puffin Phono DSP By Parks Audio
By Mike Harkins
In this product review article, Mike Harkins puts the
Puffin, a next-generation phono preamp, under the
microscope. The design adds a programmable DSP
and truly takes the concept of a phono stage to a
different level.

48 Build a Passive Moving-Coil Step-Up Device
By Gary Galo
After reviewing other products using Jensen
transformers, Gary Galo decided to build his own
step-up device and now shares his experience in this
project article.

54 Getting Started With Automotive Audio Bus (Part 3)
Designing In A2B
By Brewster LaMacchia
The first two parts of this article examined the overall
A2B system operation and how its features can enable
new types of digital audio applications. This part takes
a deeper look at A2B data transport and Analog Device
Inc.'s AD242x series of parts.

Sound Control
16 Acoustical Design Of A Multi-Purpose Room
By Richard Honeycutt

Audio Scope
22 Simple Improvements To Legacy Differential
Transimpedance to Single-Ended Audio DAC Output Designs
By Michael Steffes

Hollow-State Electronics
59 Circuit Designs For A Hollow-State Mixer
The Development of Recording Mixers
By Richard Honeycutt

Article Update
64 Comparing IMD (and THD) Measurements
Following Michel Nieuwenhuizen's
two-part article that was published in
audioXpress' October 2020 and November
2020 issues, we received a letter from
Burkhard Vogel with a question that
motivated a reply from the author.

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