Field Report: Prism Sound Dscope Series III

Perhaps better known for its Dream Series of A/D and D/A converters and Maselec high-performance analog processors, Prism Sound started developing the Dscope series of test instruments a few years ago, initially for its own in-house needs. Prism Sound recognized that manufacturers, researchers and studios could use a cost-effective, high-resolution audio test system with automation capabilities, and so Dscope was born. After intensive beta testing, the latest version — Dscope Series III — is now ready for full release.


This test system interfaces to a Windows PC via a single USB connection. The hardware provides stereo test signals in analog and digital formats, analog and digital stereo inputs for return of the tested device, digital-reference sync input and output, and monitor outputs for its signal generator and analyzer functions. The Dscope Series III application (currently at version 0.99) provides the system's control and read back. Without the controlling computer and software, effective audio testing cannot take place.

While the Dscope can be rackmounted with the appropriate hardware, its approximate 12" x 9" footprint makes for a good fit with a host laptop computer, thereby creating a portable, no-compromise audio test system.

Performance at a glance
Small, portable design
No hardware calibration needed
Wide range of test functions
Compatible with other Windows programs
Stereo I/O

A basic system signal flow chart is shown in Figure 1. The stereo analog generator provides parallel-output XLR and BNC connectors; the digital generator outputs are on XLR, BNC and Toslink optical ports. Analog and digital returns from the tested unit are provided in the same connection formats, while sync-reference inputs are only offered on XLR and BNC. Monitor outputs are via BNCs, and as an additional benefit for mobile applications, the system's headphone output and internal speaker offer a quick check of what the unit is doing. A front grounding post is provided. The rear panel has a reference-sync output on BNC and XLR and the USB connection to the host computer. Also on the rear is a DSNet connector to network multiple systems under a common host, with a four-wide DIP switch to set unit addresses in DSNet.

Up and running

Because the system requires a hardware unit, Prism Sound was able to forego copy protection. Simply connect the USB port on the hardware unit to a PC running Windows 98 or 2000, install the application from CD and start it. The hardware unit is immediately recognized, and the Dscope workspace and toolbars appear on the screen.

On startup, the user sees an empty workspace with a set of menu selections and buttons. Most of these open tileable, non-modal dialog boxes to set I/O parameters, generator signal characteristics and display analysis results. With these, any desired test, including sweeps and measurements of AES-3 signal quality, jitter and rise/fall times can be quickly set. For example, to test a stereo A/D converter, plug the analog outs (XLR or BNC) to the ADC's input and connect a digital out (XLR, BNC or optical) to Dscope's digital input. For system validation, the signal generator outputs can be looped back to analyzer inputs using internal relays or external cabling.

In the software application, open the dialogs for signal generator, digital inputs, signal analyzer and continuous time detector. This setup allows the user to control test signals, determine the digital return's integrity, and read level and noise/distortion in the converted signal. Basic audio test bench operations also can be performed.

On the next level, a user can enable the Trace window, which overlays display of the raw waveform with residual noise and distortion signals with contrasting color traces. More powerful, this offers the option of an FFT frequency analysis to view the spectrum of the raw signal or of the distortion analyzer's residual output. The residual also can be routed to audio monitoring, allowing quick analysis by ear of even the lowest-level distortion components.

Other windows provide detailed views of the AES/EBU signal with a clear indication of signal jitter and the eye pattern, which indicates the basic integrity of digital audio data transmission. This display is vital to evaluate digital audio routing and distribution components. The jitter component also can be demodulated and routed to the analyzer input, showing the exact amplitude and spectrum of sample-clock jitter.

The application's full capability for signal sweeps, across amplitude and frequency, allows the user to quickly profile a device across the full-range signals. Results can be viewed graphically, printed or recorded as tabular data.

For device qualification, such as D/A converters and digital mixers that receive digital audio information, the system's digital-output controls provide for controlled degradation of the carrier signal, applying defined percentages of jitter (with various spectral characteristics), as well as differential or common-mode interference. These capabilities are essential to characterize the robustness of a digital audio component or system.

The system provides such a wealth of information that finding an optimal Windows configuration onscreen can be challenging. Fortunately, the software's multiple pages allow various panels to be distributed sensibly, with alternate views of information. Configurations of screen displays can be saved along with full system setup information.

Scripting features

The Dscope provides an entire bench of audio test equipment in a single, portable system. But the whole point of connecting a set of audio instrumentation to a computer is to hook it to a computer. This product's primary customers are manufacturers, researchers and large station and network facilities that need to measure the performance of large amounts of audio equipment, as efficiently as possible, and collect the results into reports and statistics.

The Dscope III architecture, showing the system’s overall flow.

The system includes a detailed scripting environment that is based on Windows Visual Basic Script (VBScript) and OLE. Every setting and reading the unit is capable of is accessible via a comprehensive set of VBScript methods and properties. Scripts can be executed by an operator or in response to any system event defined in an Event Manager window. Because most major Windows applications support the VBScript and OLE interfaces, marrying Dscope to computer and network systems becomes quite simple.

Of course, with hundreds of application-specific calls available, it is easy to get mired in documentation. Luckily, Dscope's Script Editing window lets you drag-and-drop individual methods and properties into a shell from a well-organized hierarchy. For example, you can read a signal's frequency at the A input while writing its value into an Excel spreadsheet. This powerful system can be applied to an endless range of manufacturing, research and studio support applications.

The Dscope products continue to evolve. Recently, Prism Sound announced 192kHz sample rate support, and all Dscope III units in the field will receive free updates. The company also introduced a multichannel router that mates with the Dscope to facilitate multichannel measurements.

Prism Sound

The Dscope Series III is a powerful audio test and measurement system, with high performance and full automation capability, in a compact, roadworthy package. Offering a combination of analog and digital source and input capability (especially with the ability to perturb the digital output carrier and examine the results), the Dscope matches the capabilities of all but the top-of-the-line competitive products.

Hall is a technology consultant in San Francisco.

Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.

These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.

It is the responsibility of Radio magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.

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