Cambridge Audio CD Player Uses Blackfin® to Extract High-Resolution Sound from Standard CDs
England's Cambridge Audio has long been at the forefront of British hi-fi, delivering some of the industry's most innovative and technologically advanced products to consumers for nearly forty years. The company's Azur CD players – and indeed other hi-fi and home cinema separates – have received critical acclaim from the world's leading hi-fi and home-cinema consumer and trade magazines as well as the national press. However in the case of the 840C – the company's foray into mid- to high-end CD players – Cambridge Audio chose to partner with external technology specialists to help add differentiation to its flagship model.
ANAGRAM Technologies, of Switzerland, is one such technology specialist. ANAGRAM develops digital audio intellectual property (IP) that lets OEM customers like Cambridge Audio build audio products that can occupy an extremely seductive market position – audiophile sound quality at competitive costs. The newest product in the Cambridge Audio Azur lineup – the Cambridge Audio Azur 840C Upsampling CD Player – contains a highly sophisticated Q5™ Upsampling DSP that was developed jointly with ANAGRAM. This CD player extracts the most amazing high-resolution sound quality from standard CDs, revealing a level of detail never imagined possible from non-Super Audio CD (SACD) source material.
ANAGRAM licensed its IP to Cambridge Audio, which Cambridge Audio then integrated into its product with further customization. With the kind of discerning selectiveness rarely found beyond audiophile circles, ANAGRAM and Cambridge Audio selected all Analog Devices parts for the design, which included a Blackfin ADSP-BF532 signal processor and two AD1955 DACs. "We chose the Blackfin ADSP-BF532 processor as the basis for the Cambridge Audio consumer electronics application mainly because of its price/performance ratio in the under 20K-unit volume range," said Tim Llewellynn, VP Sales and Marketing, ANAGRAM. "The processor had enough internal memory to handle all of our audio algorithms so we didn’t need to buy external SRAM. And it offered enough performance for us to run very high-quality audio processing algorithms that significantly improve sound quality. We simply could not find a cheaper, more powerful processor on the market for digital audio applications."
Azur 840C Upsampling CD Player
The Cambridge Audio Azur 840C Upsampling CD Player delivers unseen levels of performance and engineering excellence to mid-end price point consumers. It features the Q5™ Upsampling technology, which is part of the upsampling DAC developed with ANAGRAM. The system intelligently interpolates 16-bit, 44.1kHz CD data to 24-bit, 384kHz data through the use of a Blackfin ADSP-BF532 signal processor. The Blackfin then feeds two, 24-bit ADI 384kHz AD1955 DACs in dual differential formation. Each ADI DAC handles a single channel for excellent stereo imaging, operating fully in differential mode for ultra low distortion and noise.
"The inclusion of upsampling technology brings about a huge benefit," said Simon Hewitt, Cambridge Audio's Director of Marketing. "As well as 24-bit, 384kHz interpolation, the 840C also plays host to a multitude of features unheard of at this position in the market. Our partnership with ANAGRAM and Analog helps continue our philosophy of constant innovation whilst maintaining unrivalled value for money. We believe this flagship model will really shift our brand proposition taking the Cambridge Audio moniker to the next level."
Why Blackfin?
When ANAGRAM was looking for a vendor to provide a signal processor to drive its DAC IP, the company was sold on ADI's strong reputation for high-quality audio processors and mixed-signal products that deliver exceptional performance and value. "We work with leading DSP and FPGA providers to bring our technology to our clients with the highest value proposition," said Llewellynn. "We feel that ADI's audio conversion signal chain offerings are superior."
With ADI as the selected vendor, the Blackfin ADSP-BF532 became the frontrunner as processor. "The Blackfin combines great audio DSP processing and MCU controller functionalities, enabling us to deliver a complete high-end audio D/A subsystem on a single chip for less than $5USD," said Llewellynn. "This level of performance has never been available at such a low price level."
The Blackfin ADSP-BF532, a 400 MHz processor with 84kb of on-chip memory, is a member of the Blackfin family of processors that embody a new type of 16/32-bit embedded processor designed specifically to meet the computational demands and power constraints of embedded audio applications. Blackfin processors combine breakthrough signal processing performance and power efficiency with a RISC programming model. The processors provide both micro-controller (MCU) and signal processing functionality in a unified architecture, allowing flexible partitioning between the needs of control and signal processing. "The integrated MCU/signal processor functionalities of the Blackfin allows us to control the entire system: display, HID, audio processing and system control, providing significant savings."
Rich Set of Peripherals/High-Performance Memory
The Blackfin ADSP-BF532 processor contains a rich set of peripherals connected to the core via several high bandwidth buses, providing flexibility in system configuration as well as excellent overall system performance. The general-purpose peripherals include functions such as UART, timers with PWM (pulse width modulation) and pulse measurement capability, general-purpose flag I/O pins, a real-time clock, and a watchdog timer. In addition, the processor contains high-speed serial and parallel ports for interfacing to a variety of audio, video and modem codec functions; an interrupt controller for flexible management of interrupts from the on-chip peripherals or external sources; and power management control functions to tailor the performance and power characteristics of the processor and system to many application scenarios.
"The Blackfin ADSP-BF532 processor not only allows for extremely high quality, cost-effective digital audio processing, it also provides us with a great audio development platform for extending the life of our products," said Llewellynn. "Numerous audio decoders and technologies are available for this platform that allow our customers to integrate hot consumer technologies for faster time to market, which is critical for our large consumer electronic clients.
"We use the Blackfin ADSP-BF532 processor's SPI interface for controlling the AD1955 DACs and other audio subsystem components. And, the internal high-speed memory is critical for our audio algorithms," Llewellynn continued. "Achieving the highest performance possible within the signal processor resources was critical for this project. By utilizing the high-performance memory and processing architecture of the Blackfin ADSP-BF532, our Q5 algorithm could be optimized to deliver stereo 384kHz upsampling with better than 144THD+N for 24-bit, 192kHz digital audio input streams."
All of the Blackfin ADSP-BF532 processor's peripherals, except for the general-purpose I/O, real-time clock, and timers, are supported by a flexible direct memory access (DMA) structure. There is also a separate memory DMA channel dedicated to data transfers between the processor's various memory spaces, including external SDRAM and asynchronous memory. Multiple on-chip busses running at up to 133 MHz provide enough bandwidth to keep the processor core running along with activity on all of the on-chip and external peripherals.
ANAGRAM leveraged ADI's software and hardware development tools, which include a USB emulator and the Visual DSP++ development environment. Visual DSP++ is a project management environment that lets programmers develop and debug an application and includes an easy to use assembler, which is based on an algebraic syntax, an archiver (librarian/library builder), a linker, a loader, a cycle-accurate instruction level simulator, a C/C++ compiler, and a C/C++ runtime library that includes DSP and mathematical functions.
The ADI emulator that ANAGRAM took advantage of used the JTAG test access port of the ADSP-BF532 processor to monitor and control the target board processor during emulation. The emulator provides full speed emulation, allowing inspection and modification of memory, registers, and processor stacks.
As for the future, ANAGRAM plans to stick with the Blackfin ADSP-BF532 processor. "With Blackfin ADSP-BF532 processor's MCU and I/O capabilities, we'll be able to upgrade our design to incorporate more system functionality, which will further reduce costs," said Llewellynn. "Q5 already forms the basis for cost-effective, high-performance audio D/A subsystems at Cambridge Audio and other OEM customers. It can integrate SACD and MP3 decoding functions if needed, and delivers spacious, richly detailed sound at price levels never before possible. We see the Blackfin ADSP-BF532 as the ideal platform for our future developments and the next revolutionary step, which is the integration of surround sound systems and digital power amplifiers."
For more information about ANAGRAM Technologies SA, please visit ANAGRAM Technologies.