A 50W/Channel Composite Amplifier

In this often mentioned project published in audioXpress, April 2001, the author explores the advantages of composite amplifiers and provides a detailed description on how he built his 50W per channel unit. A composite amplifier (also called nested-feedback amplifiers) consists of two or more operational amplifiers cascaded together with a negative-feedback loop around the entire network. Read the complete article now available online.

In this article from audioXpress archives, originally published in July 2003, Charles Hansen describes four hybrid power amps that anyone might consider for their own designs. Starting from the idea that an op amp provides both a differential input stage and high overall gain in one package, Hansen explores the ramifications of using an op amp as a combined input and voltage amplifier stage in power amplifiers. As he writes, “I did not build the four amplifiers shown in this article, but I did run a SPICE simulation to verify that they did perform as audio amplifiers."

Based in Yorkshire, England, Ivor Drawmer’s company has a long history of audio processing innovation and brilliant audio circuits. In recent years, Drawmer has been working on some brilliant monitor controllers and monitor preamps for studio work. Complementing those new studio systems, Drawmer now introduced its high performance CPA-50 compact Class D amplifier, delivering 25W rms per channel into 8 ohms (50W rms per channel into 4 ohms) or working as a 100W rms into 8 ohms monoblock which allows bi-amped or bridged modes.

In 2008, Nelson Pass submitted an article on its new F5 power amplifier design to audioXpress. At the time, he wrote: “I feel that it’s important to support AudioXpress, a magazine with which I have a 35 year history, and which also serves as a mainstay for the DIY community. Lately they have kindly printed projects that I had already posted on the web, but I decided that they deserve a little better than that.” Effectively, the F5 project was published in May 2008 and had a huge impact on the global DIY community and certainly contributed for the fact that audioXpress is still around today.

Recently shown at InfoComm 2016, the all-new VMA Series mixer/amplifiers by JBL Commercial, have been developed specifically for global markets demanding cost-effective solutions for commercial audio installations. Perfect for applications that require quality equipment at an affordable price, VMA Series mixer/amplifiers feature both 4 ohm/8 ohm and 70V and 100V output with convenient features, including a Bluetooth and USB media player, independent bass and treble controls for each output channel; paging chime; and priority muting.

Responding directly to the needs of the installation market, Lab Gruppen unveiled two new amplifier families during InfoComm 2016. The new LUCIA amplifiers follow the highly successful launch of LUCIA 70 V output models during last year’s InfoComm show now with three new LUCIA 60 W power models, all with configurable DSP features. The company also expanded its D Series advanced install-dedicated amplifier platform with the introduction of three slimline models.

Following earlier presentations at trade-shows, Hafler (a division of Radial Engineering Ltd.) announced the new P3100 2-channel amplifier will start shipping in July 2016. Designed for both studio recording and home listening, the P3100 follows David Hafler’s philosophy of offering the very highest quality at an affordable price point, and signals the return of a legendary brand following Radial’s acquisition of the Hafler brand from Rockford in 2014.

During the next edition of the InfoComm show in Las Vegas, NV, the Italian audio manufacturer will promote valuable training sessions, providing knowledge to maximize the potential of Powersoft amplifiers in Dante-based environments, fixed installations and voice alarm applications. The first training series takes place during the Dante Networking World event on Tuesday June 7.

Following its first presentation at the CES 2016 in Las Vegas, at the High End 2016 show In Munich Nagra Audio Technology Switzerland introduced the new Classic INT, a new integrated version of Nagra’s Classic Amp, now in production. The Munich presentations also included the Nagra HD Amp Statement power amplifier, and a preview of an expanded Classic line of components, including a Classic Tube Preamp and the new Nagra Classic DAC USB converter with DSD 2X and DXD support.

Harman’s Mark Levinson had much to show at the 2016 High End show in Munich. Adding to the 519 high-resolution and streaming audio player, and the 526 dual-monaural preamp with high resolution DAC and phono stage, both previewed at CES 2016, the revitalized company now introduced the 523, a version of the 526 without the DAC, and launched the 585 dual-monaural integrated amplifier with Precision Link DAC, and the 536 and 534, monaural and dual monaural amplifiers.