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Testing ConvertersHOME/SOLUTIONS/CONVERTERS

Testing A/D and D/A converters is frequently needed, now that they are prevalent in virtually every piece of audio gear. Does that 24 bit converter have 24 or 16 bit performance? Is the analog output linear at low levels? Converter tests inherently require cross domain measurements, i.e. both digital and analog audio signals and analysis. Common audio tests on both A/D and D/A audio sections include level, frequency response, phase response, noise, distortion, and linearity. The electrical signal quality also needs to be tested for voltage level, waveform shape, eye pattern, clock frequency, and jitter.

Chip-level converter testing requires an interface with extensive flexibility to cover a wide variety of logic levels, data formats, and clock settings. For example, TTL levels of 5.0 and 3.3 volts, as well as CMOS levels down to 1.8 volts need to be accommodated. I2S serial bus connectivity should be a standard feature. Internal or external master clock, bit clock, and word clock need to be provided. A very important feature is configuration via software instead of via hardware. This lets you easily save and recall settings and helps avoid costly errors.

Audio Precision’s PSIA-2722 provides chip level connectivity with all these features and more, and is designed to be used with AP’s 2722 audio analyzer (as well as the discontinued System Two Cascade and Cascade Plus). In addition, the 2722 can induce impairments, such as excessive jitter or low voltage, to test a converter’s ability to handle poor signals. Audio Precision’s ATS-2 with the Performance Option can also induce impairments, but can’t connect to the PSIA-2722 to do chip-level testing.

Common Challenges

  • Be careful to observe good RF cabling practices when connecting at the chip level.

Tips for Optimum Testing

  • Testing state-of-the-art converters requires a state-of-the-art audio analyzer. Audio Precision’s 2700 Series has the best performance of any audio analyzer in the world, exceeding the best converters available.
  • Many converters are available on evaluation boards that can be connected directly to the PSIA-2722.

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