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Methods of power

Power amplifier manufacturers are using new energy-saving techniques to make their products more efficient, environmentally friendly and easier to transport. Simon Duff looks at some of the trends and manufacturers that are making a difference.

Power amplifier manufacturers are using new energy-saving techniques to make their products more efficient, environmentally friendly and easier to transport. Simon Duff looks at some of the trends and manufacturers that are making a difference.

Last October, Bon Jovi played to 45,000 fans at the River Plate Stadium in Buenos Aires. Little did the fans realise that the sound system used for the concert saved 10 tons of C02 emissions due to the biofuel generator powering the system. At the heart of this environmental friendly system were 60 Powersoft K8 and K10 Class D amplifiers.

In a sound system, amplification is naturally by far the biggest consumer of energy. Class D, in a nutshell, is more efficient than conventional Class AB and tends to be lighter and smaller. Open up the casing of a traditional power amp and there is a transformer, usually made of copper – the reason why traditional amps are really heavy – and circuits. The pro-audio industry is now waking up to the fact that its amplifiers, combined with cutting-edge software, can significantly reduce energy consumption, creating big savings on budgets and environmental strain. At the same time, designers needs to make sure that these changes don’t equate to sacrificing audio quality.

Powersoft is branding what it calls Green Audio Power with the aim of enabling venues to reduce their carbon footprint and, as a welcome extra, cut down the cost of electricity used by the amplifiers themselves. “We have managed to maximise efficiency of our amps, meaning that we draw a minimum of power from the mains, while simultaneously delivering a maximum of top-quality output power. In fact, we are way above average in efficiency, consuming literally only fractions of many of our fellow competitors,” says Thomas Mittelmann, business development manager at Powersoft.

The Florence-based company has adopted Power Factor Correction (PFC) technology that enables power amplifiers, studio monitors and powered subwoofers to reach levels of performance previously unattainable. This is achieved by storing amps of instantaneous reserve for peak current demand. The benefits produced by the adoption of this technology in terms of energy savings and lessening the global warming impact are approximately 40% compared with amplifiers without PFC for the same output power.

Mittlemann adds: “Powersoft has clearly mastered PFC technology. Class D alone is not rocket science anymore, but with Class D alone at high power levels there is always a trade-off for sound quality, as it introduces ripple effects on the signal, and therefore requires quite a big filter set at the output stage. We have also patented a set of output filters design with smaller and unique filters that make Class D sound really good. We have had a good grip on these features from day one.”

The drive to eco-friendly systems is resulting in greater choice for buyers and some innovative fast-selling models. Lab.gruppen has always focused on the environmental impact of processes and the products it makes. Tim Chapman, head of marketing, comments: “This is a major area for us. Take, for example, the new sound system at Lord’s cricket ground in London, which Lab.gruppen was involved with. It uses 30% of the energy of the previous system and there are plans to better the figure.”

At the core of Lab.gruppen’s design of the flagship PLM 20000Q (launched last year) was a completely new approach to power supply architecture, enabling the delivery of large amounts of burst power when required, but with a low and consistent mains current draw. By recognising the fact that an amplifier typically isn’t required to deliver more than an eighth of maximum power in a real-life live music situation, and often much less than this, PLM 20000Q’s design allows it to store sufficient power to be available on tap, delivering peak bursts when required. This could typically be on the beat of a kick drum, for example, without a significant corresponding peak in current draw. In fact, it delivers 400W of burst power per amp drawn from mains, which the company claims is more than twice that of any competitor.

This performance characteristic allows it to satisfy the power demands of very large-scale touring PA systems, such as U2’s 360º tour, without the need for additional on-site electrical generators – with all of the transportation and operating diesel consumption that this involves. It’s worth noting that this approach and the resulting efficient performance will be introduced to the installation amplifier market at a much lower price point, when the new E Series is launched later in 2011.

Efficient offerings

Similarly EVI’s latest generation of multichannel Dynacord DSA and Elecro-Voice Commercial Power Amplifiers are designed to be power efficient. Oliver Sahm, EVI’s director of pro audio technical support EMEA, says: “Each channel can be configured by software to provide exactly the power required by the connected loudspeaker, not too much and not too little.” Innovative Dyanacord technology is behind the multichannel DSA 8405/8410/8805 Class D power amplifiers. Each channel can be switched individually to provide 500W respectively – 1,000W at either two ohms or four ohms. The Power Remote connector makes the task of remote controlling the power amplifier as well as switching it on and off simple.

Turning to English manufacturer MC2, the Devon-based company that merged with XTA in 2007, is currently working on a range of DSP amplifiers due to be available during 2012. For the present its E series amplifiers continue to sell well; all have lightweight power supplies, and the E90 and E100 are Class D designs. This results in output stage efficiencies, typically in excess of 91%, meaning that the E100 will carry on delivering maximum power into 2 ohms in the most demanding of environments (all channels are driven with a very low crest factor of approximately three), where other amplifiers would have begun to limit considerably, or self protect.

“Various proprietary technologies have been utilised in the design,” comments Bill Woods, group director of sales and marketing. “These include a Hybrid Dual Loop Feedback system (HDLF) for load independent, accurate audio reproduction, a high-performance Active Energy Steering Circuit (AESC), custom drive circuitry and magnetic components to ensure highly efficient, high-power, low-impedance operation without compromise.”

The E100 also achieves a maximum plug-to-plug conversion of 86% of the power consumed, as each power converter within the E100 has been optimised for maximum efficiency while a resonant PSU dramatically cuts power semiconductor losses within the main power supply.

A welcome return at this year’s Prolight + Sound was the celebrated C-Audio name, under the new ownership of Proel Group and managed by loudspeaker manufacturer Turbosound, which was itself added to the Proel portfolio in 2007. The opening gambit of this new C-Audio era takes the form of four competitively priced GB series amplifiers. All feature the same compact 2U rackmount format, but range in output power from the GB15 at 900W per channel at 4 ohms, through to the GB20 at 1,100W per channel, the GB35 at 1,800W per channel, and the GB50 at 2,500W per channel. Other features include a Lightweight Switch Mode Power Supply (SMPS), selectable input sensitivity and frontpanel LCD display screens which provide operating information including gain, heatsink temperature and protection status.

QSC has addressed the issue of reducing weight in the design of its premium PowerLight 3 Series Class D amplifiers. Three models range in power from 1,250W to 4,000W per channel at 2 ohms, all in two-rack space chassis that are only 40cm deep and weigh 10kg. Their comparatively low weight and footprint is one of the reasons why they were chosen for a recent install at the new 600-capacity club, Under the Bridge, part of the Stamford Bridge complex, home of Chelsea Football Club (see PSNE May, page 39). A record number of 66 were installed. XL Video’s Ian Woodall worked on the design and install of the sound system. He is unequivocal in his reasons for preferring QSC: “Knowing that there would be five 42U drive racks alongside other technical racks, in a combined space, we were concerned about the heat output, and it was the heat dissipation of the PowerLight 3 Series that firstly impressed,” confirms the installer. “In addition to the performance, another key issue was that they are light weight and that impacted heavily on the load in.”

Install innovation

Fifteen years ago Bose Professional Systems started a research project aimed at solving the challenges of fixed installations and aimed to come up with a modular approach. The culmination of that work is a product called RoomMatch, introduced in May to a select number of audio professionals at a theatre in Istanbul.

The idea behind it is relatively straightforward. Conventionally when users hang an array of loudspeakers in a room they use identical cabinets and angle, amplify and equalise them differently to produce the required coverage. With RoomMatch design of the system is created with a palette of 15 different loudspeaker modules each with different dispersion characteristics. Depending on the requirements of the room, users select any combination of those cabinets to hang together. This gives each project a bespoke feel to it.

The accompanying PowerMatch PM8500 amplifier is an eight-channel amp using only two units of rack space. Its total output power is 4 kW, or 500W per channel. However it is very flexible in that users can bridge pairs or even quads of channels together to give 1kW or 2kW accordingly. It will also power 100V line circuits with built-in digital signal processing. A dual feedback loop architecture continuously monitors and controls the current and voltage to help prevent circuits from being overdrawn. It also combines the sound quality and reliability of the best Class-AB designs with Class-D efficiency. Bose PeakBank power supply incorporates proprietary regenerative four-quadrant design with fast-tracking PFC. The PowerMatch Planar Magnetics transformer integrates transformer windings with the circuit board, thus increasing reliability and dramatically reducing the weight of the transformer and therefore the product.

Crown has also been pioneering new ideas aimed at the fixed install market. At InfoComm 2010 it introduced ComTech DriveCore Series amplifiers, which started shipping in May this year. Four models are available offering up to eight channels and 150W per channel in a one-unit chassis without a fan. The ComTech DriveCore amplifiers feature the Integrated DriveCore technology chip that offers greater than 90% efficiency with no compromise in performance, boasting a signal-to-noise ratio of 110dB. DriveCore also has patented feedback and protection circuits integrated into the silicon for fast and accurate response. Each of the four amplifiers in the series weighs only 10lbs.

“The ComTech DriveCore introduction is destructive in the sense that it makes everything that has come before it obsolete. It’s introduction is a watershed event in amplifier design and manufacturing in every aspect from performance, weight, heat generation, and efficiency,” states Marc Kellom, vice president of marketing for Crown. As part of Harman International, Crown has more research and development at its disposal than all of its competitors combined. This introduction is a clear demonstration of our determination to out-innovate and outperform the competition while providing our customer base with unmatched value.”

Camco launched the new Vortex V8 Silver Series high-performance Class H amplifier last year. It contains an integrated Digital Signal Matrix and a Network Operation System called Unos. With more than 10kW of continuous power in 2-ohm or 4-ohm mode it also shows off a new design aesthetic and streamlined user interface. The most notable feature is the absence of any control knobs or switches, front or back. In this new format, the control of all parameters is via screen display and gain sliders. Reiner Sassmann, managing director, comments: “Such a clean and practical approach reduces wear and tear factors on moving parts, not to mention developing a more progressive approach to function and form. V8’s flexibility also extends to intelligent input routing; the signal path is direct from input to output bypassing any unnecessary A to D converters. Because the network input is linked directly to the amplifier channel, operators can choose to run the system full in the analogue or digital domain.”

Looking to the future it seems clear that Class D amplifiers coupled with DSP networking skills will inevitably result in more multichannel amplifiers appropriate to a number of applications. Another important factor has to do with cost: the continuous increase in the price of raw materials such as iron and copper used in traditional power amps, combined with the reduction in the costs of Class D and SMPS technologies, suggests that in the future traditional amplifier technology will be replaced almost completely by the new ones in all areas of the pro audio and MI market places. This will bring big advantages not only to the users having to carry less weight around, but also to the environment, thanks to the energy saving.