Audio Myths: Feedback Re-Entrant Distortion. Should We Worry?

There are many aspects of negative feedback in audio that are the subject of continued discussion. Jan Didden continues to debunk more Audio Myths. This article addresses re-entrant distortion. The idea is that, since negative feedback sends some of the distorted output signal back to the input, this already-distorted signal would only get more distorted by going through the nonlinear amplifier, over and over again.

The launch of the Lyngdorf MXA-8400 8-channel amplifier, introduces an extraordinarily powerful, power-efficient, and ultra-linear multichannel amplifier, incorporating Purifi Eigentakt technology and delivering 8 x 400 watt. The MXA-8400 also features the new, highly efficient Lyngdorf PowerPerfect power supply with Channel Balancing Technology and integrated mains power decoupling and filtering.

AudioControl will be attending CEDIA Expo in Denver, CO, reenergized and focused on presenting a range of innovative solutions. Designed based on market trends and feedback from system integrators, AudioControl’s newest amplifiers and mini-chassis surround receivers deliver the latest technologies while creating opportunities for integration professionals. The company will introduce Dante network connectivity to its successful AudioControl Director Model M6800 multi-zone amplifier, and launch two compact-chassis surround receivers to deliver Dolby Atmos and DTS:X Pro processing in any zone.

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.

AVPro Global, a company that started as a distributor, and evolved to create its own brands of audio/video installation products, display calibration and HMDI cables, has announced the acquisition of the Home Audio division of AudioControl from AAMP Holdings, an aftermarket car audio company from Florida who had acquired the Seattle, WA company in April 2022. AVPro Global says that the AudioControl Home Audio Division makes sense in its strategy to accelerate its business in residential and commercial distributed audio and media rooms.

The new NCx500 amplifier board from Dutch manufacturer Hypex Electronics is the first of a new NCOREx family of modules that evolves from the extremely popular NCORE Class-D amplifier technology, one of the most successful options among high-end audio and studio monitor brands. Stuart Yaniger was able to spend a few weeks with this next flagship for OEM applications. How will this improved NCOREx technology measure up? And will it deliver the "x" times improvements over the proven NCORE? Stuart shares all the juicy details.

This article expands the conversation around feedback theory for electronic circuits and audio amplifiers. Do we "really" need wideband open loop in audio amplifiers? The subject came up at the 154th Audio Engineering Society (AES) convention in Helsinki, Finland. Looking at the frequency domain, not necessarily, Jan Didden argued. In this article he looks at the question in the Time Domain. Narrow Bandwidth, High Open Loop Gain Amplifier versus a Wide Bandwidth, Low Open Loop Gain Amplifier in the Time Domain.

Although feedback theory for electronic circuits has been established for over a century, it is still a subject for discussion. This short essay is an attempt to shed some light on one of those recurring controversies. The subject came up at the 154th Audio Engineering Society (AES) convention in Helsinki, Finland. Audio amplifiers are basically integrators or, if you will, low-pass filters. That means that at some frequency, their open-loop gain starts to fall off. With that, the loop gain available for feedback also starts to fall off, leading to a diminishing of the curative effects of feedback: distortion starts to rise, gain accuracy starts to drop, output impedance starts to go up, etcetera.

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.

audioXpress July 2023 provides an updated market and technology overview of Audio Amplifiers, includes the review of the Hypex Nilai500DIY 500W Power Amplifier Kits, a visit to Dutch company Grimm Audio, and an interview with Rémi Guastavino to discuss the new GRAS EQset measurement microphone series. Plus a review of the new WiiM Pro Music Streaming System, a new article series about Bass Reflex speaker performance, and a lot more.