Analysis

DAC and pre-amp brings cost and performance advantages to AVR and sound card design

21st May 2009
ES Admin
Diodes Incorporated has introduced an 8 channel DAC and pre-amplifier chip offering designers of audio video receivers and add-on sound cards the opportunity to reduce component costs while at the same time improving audio performance. Part of the Zetex Direct Digital Feedback Amplifier product line, the ZXCZM800 will dramatically reduce circuit complexity, and in high performance differential mode, will deliver a dynamic range (DNR) as high as 126db. The outstanding performance of the DAC solution complements that of digital amplifiers created using the DDFA chipset.
In both consumer and professional audio product designs currently depending on the use of multiple quality 2-channnel DACs to achieve mid- to high-level audio performance goals, the ZXCZM800 offers the means to significantly reduce component inventory and PCB size. At the same time, with typical mid-range AVRs and sound cards currently producing a DNR of 112dB, the Diodes chip is more than capable of matching or improving upon existing product sound quality.



For product designers looking to expand a product’s feature set, the ZXCZM800 also offers the option of pre-amplifier DSP features, simply programmed using an existing system host processor. For example, by integrating a digital volume control function, operating on a per channel or and/or all channel basis, the chip is able to further simplify product design, improve performance and reduce cost. A digital multiplexing function enables additional digital inputs to be accommodated and simple implementation of multi-room configuration to be achieved. 14 user programmable biquads per channel facilitate filter functions such as parametric EQ.



In terms of DAC performance metrics, the ZXCZM800 offers a maximum resolution of 32 bits, meaning more headroom and less impact on performance with higher input audio data resolutions. Maximum sample rate is up to 192kHz and DNR in single ended operating mode is 120dB. For distortion and noise, figures less than 0.001% are typical for single ended mode, less than 0.0004% in differential mode.



The ZXCZM800 DAC and pre-amplifier chip is supported by an 8-channel demonstration board, details of which will be made available for volume production DAC and preamplifier designs, and includes circuit diagrams, bill of materials and Gerber files.

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