With tens of millions of units sold every year, testing the quality of consumer MP3 devices is vital. Consumers' perspective of your brand can be badly damaged from sporadic quality or DOA devices. From a business perspective, testing ensures that your vendors and contract manufacturers are providing the quality of service they were paid for.
Audio Precision has developed the High Speed Tester (HST) program to facilitate rapid mp3 player testing with its 2700 Series and ATS-2 audio analyzers. The HST gives pass/fail results with reports in just a few seconds, so it's ideal for production line testing.
HST uses a custom multitone created by Audio Precision, which provides DC offset, frequency response, phase response, total complex distortion, noise spectrum, and crosstalk results simultaneously. This makes testing extremely rapid and accurate.
Audio Precision's analyzers are extremely flexible. You can produce your own multitone test files and automated testing programs to meet your specific requirements, if you prefer. All of Audio Precision's analyzers, including the 2700 series, the APx500 series, and the ATS-2 are ideal for testing mp3 players.
- MP3 players are playback only, so you'll need high quality test tones. Your analyzer must be able to trigger when it hears the tone, even if the MP3 player adds distortion. Audio Precision's instruments excel at this.
- You'll need to find the optimal headphone volume setting on the player, and set each unit's volume control to the same place to get repeatable results.
Tips for Optimum Testing
- Check performance with a 32 ohm load, to stress the headphone amplifier under real conditions.
- Determine if you need a filter. The APx Series has a high tolerance for out of band noise, however a filter may still be required. To find out if you need a filter, the best way is to compare results with and without a filter in line between the amp and the analyzer. A filter, such as the AUX-0025 or AUX-0100, should always be used with the APx585 or APx586 to block the DC voltage that is present on class D amplifier outputs. The APx525 should have AC input coupling selected if the filter is not used.
- Turn off any built-in headphone volume limiter, EQ, bass boost, or other effects.
- Test with both mp3 and uncompressed wav files, if the player supports both formats.