Meridian selects Dscope Series III audio analyser

Meridian has used a Dscope Series III audio analyser from Prism Sound to achieve what is claimed to be outstanding audio quality on its F80 transportable home entertainment system.

For Meridian, achieving outstanding audio quality was a key requirement from the outset.

The company recognised that in order to do this, it needed high-performance audio test equipment, both in its research and development labs and on its production line.

Paul Holmes, Meridian's test manager charged with designing and commissioning production test systems, said: 'For the F80, we wanted an audio test system that would allow us to fully customise and automate our production testing.

'We wanted to design a flexible, hierarchical user interface that could run our entire test sequence automatically, but which could also be manually overridden by the operator, in order to run individual tests and adjust settings on demand.

'This was an important requirement, as this approach allows our test engineers to find and fix problems much more quickly than if they had to wait for the entire test to execute, and then try to interpret pages of results to find the source of the problem,' he added.

For Holmes, there was only one audio test system on the market that could do everything he needed: the Prism Sound Dscope Series III audio analyser.

Prism Sound audio test equipment is used by many consumer electronics brands in automotive, home entertainment, personal mobile, communications and other market sectors.

The company's Dscope Series III was the ideal choice for Meridian because it offered the ability to customise scripting for the production line.

'The audio test equipment we were using on other products just couldn't handle what I needed it to do,' said Holmes.

'I thought the Dscope was an ideal solution.

'It was already being used by our research and development engineers, who have three in their department, so I knew what it was capable of,' he added.

Prism Sound's Dscope Series III is a measurement system for analogue and digital audio generation and analysis, including digital audio carrier analysis, acoustic transducer testing and testing of Windows sound devices.

This audio test and measurement system comprises a Windows PC (XP and Vista compatible) software application coupled with an external high-precision audio I/O processor for equipment-under-test (EUT) connections.

Meridian invested in two Dscope units and two multi-channel switching units for its production line and once they were delivered, Holmes spent 12 weeks designing the test scripts to suit his exact requirements.

The F80 incorporates three channels of power amplification, AM/FM and DAB receivers (UK model), optical digital output and input, headphone output, two auxiliary inputs and a DVD ROM drive, all of which are fully tested using a Prism Sound Dscope Series III analyser in conjunction with a DS-NET I/O switcher.

To ensure that customers experience only the highest quality audio visual experience, all Meridian products face a rigorous series of tests before leaving the factory.

The process starts with flying probe testing of populated PCBS, followed by soak testing of assembled units, comprehensive audio and video performance/functionality testing and ending with a human audition.

Using Dscope Series III, the F80's distortion response, frequency response, gain and noise is checked on each output channel for every source input, in addition to checking digital frame rates and channel status information on the digital outputs.

Dolby/DTS down mixing and bass management are also tested using pre-recorded tracks on a DVD test disc, and the F80's dynamic equalisation curves are checked using swept results.

Rather than exploit Dscope's rapid production testing tools such as multi-tones, Meridian prefers to use slower testing techniques, such as sweeping results and one channel at a time.

'This slows down the testing to a human level, allowing the operator to see the test results being presented in real time, and allowing the units to warm up to operating temperatures during testing,' said Holmes.

'It also enables us to verify that output devices have been correctly coupled to their heat-sinks and that thermal limiting circuits are operating at the correct cut-offs,' he added.

Holmes has created a custom user interface using Dscope Series III's script dialogue controls.

This interface allows the user either to run the complete functional test sequence by selecting the 'test go' command, or to select an individual sub-routine from the menu.

By clicking on the 'front panel - manual control' command, the user is able to configure the I/O switcher and to take over control of the Dscope.

This gives the operator the choice between a completely automated linear test sequence, or to take over manual control of a smaller subset of the test to enable rapid diagnosis of test failures and effective debugging.

In order to control the F80 during production testing, Holmes has implemented serial port communication from within his Dscope Series III automation scripts.

This facility allows Dscope to address a serial port on the host PC, which in turn is used to control the F80 via its RS232 port.

This enables F80 functions such as track selection, volume/EQ settings and input selections to be controlled from Dscope's automation scripts.

The Dscope Series III audio analyser has helped Meridian improve its production line testing for the F80, to the extent that Holmes is now considering purchasing more units so that they can be implemented on the production lines for other Meridian products.

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