EE Times Under the Hood - June 23, 2008 - (Page U34)

UTH0623DIGI_pg28_38.qxd 6/11/08 3:01 PM Page 34 under the hood: w w w. e e t i m e s . c o m D I G I T A L HOME trol any of up to 32 ZonePlayers—from the bedroom to the backyard. The ZoneBridge simplifies setup of the SonosNet wireless network and extends its range to remote locations, such as a garage or guest house. Its Ethernet jacks also bring Internet connectivity to personal video recorders, set-top boxes, etc. It retails for $99. Setup a cinch On unpacking the system, I charged the controller in its cradle. The next day, I hooked the ZP100 to a pair of oldie-but-goody Celestion 3 bookshelf speakers I had lying around. I connected one of the ZP100’s Ethernet ports to one of the ports on my wireless router, installed the software on my laptop and powered everything up. (Laptop interface software was optional.) The system immediately and flawlessly performed a software upgrade, and I was able to assign a zone name (basement office) via the computer’s desktop controller. On powering up, the controller immediately found the office ZP100, and I had full control of my system’s music archives, as well as Rhapsody and Sirius radio and Napster files. The 30-day trial connections worked without a hitch, and within seconds I was listening to U2 and Pavarotti. The sound was clear, crisp and powerful, with no detectable distortion or latency-induced artifacts. Next, I hooked up the ZP80 to my main audio system upstairs. I was quickly controlling both the main system and my basement office ZP100 using the Sonos controller. Any combination of audio streaming was flawlessly reproduced, from a single stream to multiple streams from different Internet and local storage sources. Key design choices At the heart of the Sonos system is a commitment to simplicity. The designers focused on the software interface, leveraging software to hide the technical complexity behind the audio distribution mechanism. To that end, the team made four critical design decisions early on. The first was to go with a software-upgradable approach that gives the controller a five-year expected life span and the ZP100, 10 years. A second critical decision was to use • w w w. t e c h o n l i n e . c o m Sonos’ designers needed to make the system as simple to use as a legacy audio appliance, enabling system upgrades in a rapidly changing consumer market. Multiroom audio synchronization was another hurdle, as was ensuring reliable, latency-free wireless connectivity. The design team was also thrown some curve balls, such as RF harmonic interference and problems derived from designing the motion-sensitive controller separately from the cradle it rests in. The base system, which sells for $1,000, comprises two ZonePlayers— the ZP100 and ZP80—and a single wireless controller. The ZonePlayers can access and play music formats such as MP3, WMA, AAC (MPEG-4) and WAV, stored on a PC, Mac or network-attached storage. They come bundled with customizable Internet radio stations. Built-in wired and secure wireless capabilities provide the consumer flexibility of installation at no extra cost. The ZP100 has an integrated amplifier that distributes, plays and amplifies music in any “zone” in the home. The device is said to deliver 50 watts/channel into 8 ohms or 120 W/channel into 4 ohms, with a total harmonic distortion of 0.02. (In reality, it can actually deliver up to 68 W/channel into 8 ohms). The ZP80 has no amp and instead IN BRIEF Designers of the Sonos Digital Music System took a softwareupgradable approach, allowing them to develop a solid hardware foundation that’s easy to use and provides top-notch sound and a strong wireless connection.The system works flawlessly and has the latest options, from home networked-attached storage connections to online music sources such as Napster.The addition of ZoneBridge overcomes range issues. Overall, the system is a well-implemented design that brings music into the digital age. Component focus integrates into an existing audio system or simple off-board amp/speaker setup. Either device can form the wired connection to the home network, though the ZP100 has a fourport Ethernet switch vs. a two-port switch on the ZP80. Both have digital (optical and coaxial) and analog RCA inputs and outputs. The wireless controller, which comes with a rechargeable battery that rests in its own powered cradle when not in use, has a full-color screen and powerful touch scroll wheel. It allows the user to access, customize and con- Sonos’ designers turned to a lesser-known solution for its power amplification and control circuitry by working with Tripath’s TC2000 Class T controller, supported by two STA505 half-bridge FET power amplifiers from STMicroelectronics.While Tripath no longer exists, its technology lives on. Class T isn’t a class of amplification, as such, but rather,Tripath’s spin on Class D, with a sophisticated control system to provide high-quality audio.Wikipedia provides a good explanation: Rather than using digital signal processing, Class T amplifiers use an overall loop similar to a higher-order delta-sigma modulator.While it is called a digital amplifier, the Class T amplifier is almost entirely analog; the amplifier uses a digital clock internally only to control the sampled comparator.The two key aspects of this topology is that (1) feedback is taken directly from the switching node rather than the filtered output, and (2) the higher-order loop provides much higher loop gain at higher audio frequencies than possible in a conventional single-pole amplifier. One downside is the high-frequency noise derived from the switching. However, the Sonos amplifier section has LC filters on the outputs to prevent the transfer of the noise components to the speakers. 34 Electronic Engineering Times, TechOnline | June 23, 2008 http://www.eetimes.com http://www.techonline.com

Table of Contents Feed for the Digital Edition of Under the Hood - June 23, 2008

Under the Hood - June 23, 2008 Extreme Design: SuitSat Pushes Desigers' Limits Evolution of the Smart Phone Mature Devices get Rolly Rocking GPS: Garmin Nuvi 750 vs. HP iPaq 310 Inside the Sony OLED TV Multizone Dgital Audio Flip Ultra Camcorder - An Ode to Clean Design Robot Guitar Tunes Itself E-book is a Sight for Sore Eyes Scientific Calculator Boils Down to Two ICs $100 BOM Eludes First OLPC Laptop 45 nm: What Intel Didn't Tell You Next Step in NAND Flash Evolution Surveillance on a Shoestring Hot 3G Phone Owes Debt to Analog SecurID Fob: Single-Chip Safety Net

Under the Hood - June 23, 2008

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