Perhaps better known for its Dream Series of no-compromise A/D and D/A converters and Maselec high-performance analog processors, PrismSound started developing the dScope Series of test instruments a few years ago for in-house needs. PrismSound recognized that manufacturers, researchers and studios could use a cost-effective, high-res audio test system with automation capabilities, and so dScope was born. After a year of intensive beta testing, the latest version — dScope Series III — is now ready for full release.
The rugged dScope III interfaces to a Windows PC via a single USB connection. The dScope 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. The full package, minus host computer, lists for $8,800.
While dScope can be rackmounted with Prism's optional rackmount kit, its approximate 12×9-inch footprint makes for a good fit with a host laptop computer, thereby creating a portable, no-compromise audio test system. The unit's solid construction and top-notch components exude confidence.
A chart of the basic system's signal flow is shown on page 110. The stereo analog generator outputs to parallel XLR and BNC connectors; the digital generator outs 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, dScope'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 (there isn't room left on the front) and the USB connection to the host computer. Also on the rear is a “DSNet” connector to network a range of dScope peripherals such as the DSNet I/O, with a four-wide DIP switch to set unit addresses in DSNet.
UP AND RUNNING
The dScope III system's beauty becomes apparent when you connect the host computer, install the control application and start testing devices. The control application's installation and startup could not be easier. Because the system requires a hardware unit, PrismSound was able to forego copy protection. You 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 up. 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.” (In an upcoming software release, the toolbar will be preloaded with buttons, providing instant access to a range of test configurations.) Most of these open up the tileable, nonmodal dialog boxes to set I/O parameters, signal-generator characteristics and display analysis results. With these, you can quickly set up any desired test, including sweeps and measurements of AES-3 signal quality, jitter and rise/fall times. For example, to test a stereo A/D converter, simply 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, you can open the dialogs for signal generator, digital inputs, signal analyzer and continuous time detector. This setup allows you to control test signals, determine the digital return's integrity and read level and noise/distortion in the converted signal. You can also perform basic audio test bench operations.
On the next level, you can open the Trace window, which overlays the raw waveform's display with residual noise and distortion signals via contrasting color traces. 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 can also be routed to audio monitoring, allowing quick analysis by ear of even the lowest-level distortion components. dScope can also view the time-domain trace at the same time as an FFT.
Other windows provide detailed views of the AES/EBU signal with a clear indication of signal jitter and the “eye,” 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 can also 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 you 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 dScope's digital outputs controls provide for controlled degradation of the carrier signal, applying defined percentages of jitter (with various spectral characteristics), as well as differential and/or common-mode interference. These capabilities are essential to characterize the robustness of a digital audio component or system.
The dScope system provides such a wealth of information that finding an optimal windows configuration onscreen can be challenging. Fortunately, the software's multiple pages (tabs visible at lower right) 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.
dScope provides an entire bench of audio test gear in a single, portable system. But the whole point of hooking up a set of audio instrumentation to a computer is to, well, hook it to a computer. The dScope Series III's primary customers are manufacturers, researchers and large facilities that need to measure the performance of large amounts of audio equipment as efficiently as humanly possible, and collect the results into reports and statistics. Many users will also want to investigate realms that require arcane sequences of individual measurements, correlated across time and space.
The system includes a detailed scripting environment, based on Windows Visual Basic Script (VBScript) and OLE. Every setting and reading the unit is capable of (including its motherboard temperature) 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. Want to get an e-mail when a unit or group of units fails a certain test? It's quite easily accomplished.
Of course, with dozens or 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.
The dScope products continue to evolve. At AES, PrismSound announced 192kHz sample rate support, and all dScope III units in the field will be eligible for free updates. The company also showed a multichannel router that mates with the dScope to facilitate multichannel measurements.
dScope Series III is a wonderfully 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), dScope is a credible alternative for budget-limited and high-end applications. Overall, dScope Series III offers a tremendous amount of power and quality for a very good price. If you need an integrated, automatable audio test rig, dScope is something to look at.
PrismSound, dist. in the U.S. by Prism Media Products Inc., 21 Pine St., Rock-away, NJ 07866; 973/983-9577; www.prismsound.com.
Gary S. Hall operates the world's only solar-powered piano lounge.