Book Review: Burkhard Vogel’s Slopes and Levels. Spice Models to Simulate Vintage Op-Amp Noise

Interested in accurately simulating the noise of op-amp circuits? Audio electronics expert Burkhard Vogel wrote a book that addresses this relevant topic for any audio circuit designer that doesn't want to rely just on manufacturers own models. In this review, Marcel van de Gevel explored the full book after he read Vogel's introduction, explaining that some manufacturer-supplied simulation models are way off.

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.

This article discusses how Warwick Audio Technologies designed a completely new type of transducer for high-end electrostatic headphones using the latest materials, validated with computer simulation tools from Comsol. The design process for the High-Precision Electrostatic Laminate (HPEL) transducer was first available in the outstanding Sonoma Model One, the world’s first headphones to use HPEL audio transducers, and all subsequent Warwick products, now expanding also to automotive applications. This article was originally published in audioXpress, April 2018.

The Mackie DLZ Creator is a new all-in-one podcasting and streaming audio solution for content creators that makes it easy to get professional results. The DLZ Creator podcast mixer draws on Mackie's rich 30-plus-year history of supporting creators with accessible, professional-grade audio equipment. A solution for today's creators available for $799.99, complete with Mackie’s Mix Agent technology, that easily and seamlessly assists, automates, and guides the users.

Edifier has released the W820NB Plus headphones which continue the brand's outstanding record for affordable but premium quality audio products incorporating the latest technologies. The W820NB Plus headphones are an update of the existing W820NB model, now adding support for the LDAC Bluetooth codec and earning Hi-Res Audio Wireless certification also thanks to 40mm titanium coated dynamic drivers.

When the first Amazon Echo device launched in 2014, it created a new category: The smart speaker. The Echo speakers brought the voice assistant to the home and created the perfect controller for the early "smart home." Unfortunately, almost 10 years later, voice recognition still has a long way to go, the multi-language promise is still unrealized, and Echo speakers are already everywhere - in the countries where Amazon sells them. The company even announces new models with a blog post.

CEVA announced the acquisition of the RealSpace 3D Spatial Audio business, technology and patents from VisiSonics Corporation. The acquisition of RealSpace enables CEVA to offer a complete spatial audio solution to OEMs, targeting high volume markets including true wireless stereo, OTC hearables, gaming headphones, AR/VR, audio conferencing, automotive and media entertainment.

Always pushing different concepts into every product category, JLab introduced the new Work Buds ($79.99), a true wireless stereo concept that is intended to solve the sub-par microphone clarity problem during calls. The first time this is ever attempted in true wireless earbuds, the San Diego, CA-based added a a lightweight, detachable noise-canceling boom microphone. Revolutionary or simply awkward, now there is an option.

Bang & Olufsen introduced the new portable Beosound A5 speaker. Designed in collaboration with the Danish-Italian design duo GamFratesi, the new Beosound A5 bridges northern and southern design cultures with powerful sound, meticulous craftsmanship and product longevity that Bang & Olufsen is renowned for. A work of art, this speaker sets a desirable reference for the future of audio.

When a manufacturer sends out an announcement of a new color finish or product iteration based on inconsequent novelties, it receives a strong pass from audioXpress. In this case, we truly found that these iLoud Precision Studio Monitors White Edition from IK Multimedia deserved a mention. Because the iLoud Precision series continues to be a very unique product with exceptional value that really needed white models to stand out.