Audio Myths: Feedback Cannot Fix What Has Already Happened

This article, originally published in The Audio Voice newsletter (#434), explores some practical experiments with Negative Feedback. "If I had a dollar for every time someone mentioned that negative feedback cannot work, because you cannot correct something after it happened, I would be a rich man," says Jan Didden. "Yes, it can be hard to get your head around feedback circuits for audio amplifiers. Yet, all it takes is to look around you," he adds.

The topology and the distribution of the wiring, partitioning between low power and high power circuits, grounding scheme, types of cables, protection techniques, and safety are important factors that must be considered to minimize the interference effects in audio amplifiers. This "tips and tricks" audio electronics article provides several details about inductive coupling effects in audio amplifiers and the simple way to minimize them.

An audio load is an essential piece of test equipment for any audio electronics workshop. Having created the very popular Heathkit ID-5252, more than 35 years ago, Gary Galo decided to design a new option for everyone to build now. The ID-5252 contains four 8Ω, 60W power resistors. The biggest limitation of the Heathkit load is power handling. Series and parallel combinations can be used to produce various resistances and power levels — up to 240W at 8Ω, using all four resistors. But, simultaneously testing both channels of a high-powered amplifier requires two ID-5252 units. Fortunately, the raw parts for building an audio load are easy to find.

Linear Integrated Systems, the world class producer of ultra-low-noise JFETS and other small-signal discrete semiconductors, has announced the re-release of its LSK489 discrete component with specialized parameter grading. The LSK489 is one of the world's premier JFETs optimized for use in high-end sensor front-end amplification designs, and the re-release in 2022 introduces improved manufacturing consistency.

John Melanson, senior technical fellow at Cirrus Logic, has been granted his 500th US patent, an achievement that places him among the world’s most prolific inventors. The Academy Award-winning engineer’s core contributions are within the field of audio and electronics, particularly the analog and mixed-signal technologies that have helped transform the analog world around us into the digital signals at the heart of today’s most advanced products.

Following the launch of three Ferrum products, HEM now announces Serce, a completely new digital audio platform that contains everything needed for a wide range of new hi-fi product developments. HEM is the audio manufacturing company from Poland that recently launched its own brand, Ferrum, with products aimed at high end audio enthusiasts. With Serce, HEM reinforces its position as a one-stop-shop solution for ODM/OEM audio electronics.

Charcroft Electronics, the specialist distributor and manufacturer of electronic components, has launched the Purity range of ClarityCap audio capacitors to deliver a significantly lower noise floor, with more ‘dark space’ around the audio signal, and an improved dynamic range. These features enable greater clarity for audio reproduction as well as improved spatial separation for the individual instruments and vocals. The new capacitors use the multi-strand Van den Hul cable specified by high-end loudspeaker manufacturers.

Linear Audio, the bookzine created in 2010 by Jan Didden, is now available on a USB with The Complete Linear Audio Library. We asked three Linear Audio and audioXpress authors - Gary Galo, Bob Cordell, and Dimitri Danyuk - to review it and share their thoughts. Important to know, the USB drive doesn't contain only the PDFs of published articles. It also ads additional articles by Jan Didden and others, together with materials of historical interest.

The November 2021 edition of audioXpress looks at the latest industry trends in digital signal processing, and enabling fully adaptive audio DSP experiences. Roger Shively (JJR Acoustics) writes about how the unique acoustic space of the car interior can be defined by the use of DSP, and Al Clark (CEO, Danville Signal Processing) shares his company’s journey into the development of the dspNexus DSP Audio Processor. Now available for viewing online, download and in print.

Following the cancellation of the scheduled in-person convention and activities, the Audio Engineering Society is promoting a series of online activities in order to bring its AES Fall Online 2021 Convention to a worldwide audience. Starting Monday, October 11, with live-streamed and on-demand events continuing through the month of October, all the events are included in one registration.