audioXpress Magazine - December 2020

In this issue

8 Remembering Jeff Bagby 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. 16 Acoustical Design of a Multi-Purpose Room 22 Simple Improvements to Legacy Differential Transimpedance to Single-Ended Audio DAC Output Designs 26 QuantAsylum QA401/QA451 Redefining the Compact and Modular Audio Measurement System 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 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 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 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 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. 59 Circuit Designs for a Hollow-State Mixer The Development of Recording Mixers