The Digigram VX882HR is a professional, eight-channel audio sound card. Equipment manufacturers and end-users alike will find it to be a powerful, versatile and easy-to-use interface for demanding multi-channel audio applications. It is a Windows-compatible device that is functional in recording studios and radio automation.
Digigram has created digital audio hardware and software since 1985. The HR series cards represent the company's latest development in digital audio processing. The company names its cards based on the audio configuration. The VX882HR manages eight simultaneous audio streams in and out, thus the 88 in the name. The last number indicates the audio format of the I/O. A zero is analog, one is digital and a two is both. The HR refers to its high resolution 24-bit/192kHz A/D and D/A converters.
Digigram recommends at least a Pentium III or equivalent CPU running Windows 2000 or XP with 128MB of RAM. The computer must have Microsoft Direct X runtime version 9 installed.
The card is Universal PCI bus compatible, which means it can be plugged into a 32-bit/33MHz 5v PCI slot as well as a 64-bit/66MHz 3.3v keyed PCI slot. It is also compatible with PCI-X interfaces. Interface cables can be purchased separately, but a handy, 2RU break-out-box with XLR connections (aptly named BOB) is available.
At the heart of the design is the Motorola 56321 DSP chip. Like video, digital audio devices must be synchronized to the outside world for trouble-free operation. It can be synced internally with a crystal or externally with video, word clock, linear time code (LTC) or AES/EBU. The LTC interface also enables editing software to chase video in post-production settings.
Four stereo analog-to-digital converters (ADC) allow independent control on each channel. The maximum analog input level is +24dBu. Functions like input gain, mute and balance are controlled in software. The sample rate converter operates from 8kHz to 96kHz on inputs and up to 192kHz on outputs, with data resolution from eight to 24 bits. Four AES receivers process the digital audio delivered to the separate digital inputs.
Performance at a glance
Eight analog and digital inputs/outputs
Recording sample rates up to 192kHz
Universal PCI interface
Optional breakout box (BOB)
Four stereo digital-to-analog converters (DAC) manage the job of playback. Output gain is software controlled with a maximum output level of +24dBu. There are four digital transmitters for the digital AES/EBU outputs.
Digigram works extensively with original equipment manufacturers (OEM) worldwide to marry hardware to second-party software applications. A comprehensive set of drivers comes with the card. The Software Development Kit (SDK) is a toolbox of application programming interfaces to minimize development time required to get a product to market.
The company website provides additional development resources and updates for developers. Finding driver and software downloads is easy. The VX882HR is relatively new, so the website's knowledge base is limited right now.
Basic drivers like Windows Direct Sound, Wave or ASIO are compatible with many off-the-shelf audio software packages. Users will recognize the all-familiar Windows Mixer, which becomes the intermediary between hardware and software. For those unfamiliar with the ASIO protocol, Digigram describes it as follows:
“Audio Streaming Input Output, developed by Steinberg in the late 90s as an alternative to poorly featured consumer protocols, is a cross-platform, multi-channel audio transfer protocol that has been adopted by many of the manufacturers of audio applications. It allows software to have access to the multi-channel capabilities of a wide range of powerful sound cards (which necessarily feature ASIO drivers). ASIO typical benefits are low-latency and timely synchronized overdubs, hardware monitoring management, 24-bit support and time-code synchronization.”
A Play Rec test application helps to verify that the sound card is actually working by recording and playing back basic audio files. The Digigram Control Center has an extensive set of diagnostic tools including a sine wave generator.
Everything to get started is located on the CD supplied with the card. In Windows XP it automatically opens a browser and shows a list of supported sound cards. Hardware interrupt and addresses are automatically set up at start-up by the PCI PNP BIOS.
For testing, I used an Audio Precision Portable One Dual Domain analyzer and a copy of Adobe Audition. I began my tests by setting the Audio Precision (AP) to +4dBu (about 1.227V). I began by setting a level of -18dB on the input meter. I had to lower the Windows Direct Sound mixer pot to nearly the bottom most setting. It was touchy.
A dedicated control panel is under development to be released in 2006.
Lowering my generator to -24dBu helped considerably with input control. The card performed according to published specifications and interfaced seamlessly with the audio editor I chose.
Though the VX882HR is often sold to OEMs of audio processing software and equipment, it is available through Digigram resellers worldwide.
Chestnut is assistant chief engineer at Entercom, Kansas City.
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