Antex Electronics Corp, Gardena, California has made available an advanced digital audio board with Dolby AC-2 coding, which provides real-time, compressed professional broadcast-quality stereo sound through personal computers, PS/2s and compatible computers. The new personal computer add-on board, Series 2 model SX-22, is the third audio board with Dolby AC-2 from Antex. Based on Texas Instruments Inc’s floating point TMS320C31 signal processor, it is the only board to use the Dolby AC-2 bit-rate reduction technique for high-quality compressed sound in three sample rates – 32KHz, 44.1KHz and 48KHz. In addition, Antex has included both balanced analogue and AES/EBU or S/PDIF digital input and output in the SX-22. This supports direct digital connection to professional and consumer digital audio equipment, and provides the ability for network transmission of audio in digital format without sacrificing quality. Using the advanced Dolby algorithm, the SX-22 provides real-time, direct-to-disk, storing or transmitting of two channels of high-quality – 20KHz audio frequency response – audio in only 256Kbps – approximately one-sixth the rate of most boards on the market.
Quality sound over T-1 phone lines
This means that personal computer users can now add full FM broadcast, CD-quality digital sound without sacrificing valuable disk space. And, of particular interest to audio equipment manufacturers, FM broadcasters and multimedia developers, it also means that high-quality audio sound can be transmitted over T-1 phone lines. The new Antex SX-22 features other software selectable storage formats in addition to Dolby AC-2. These include pulse code modulation and its ADPCM derivative and digital video interactive. Input resolution is 16-bit with Sigma Delta Conversion and 18-bit, 8-times oversampled output. The result is improved clarity, low noise, less interference and increased signal-to-noise performance, which more than meet the standards of professional audio mastering, broadcast automation and multimedia applications, Antex says. Unique to the Antex design is a built-in EEPROM-based software security scheme. This enables developers and system integrators to give each board a unique identification number. By doing this the SX-22 acts as a hardware key enabling developers to instruct their software to look for the Antex board. If the board is not present, the software is disabled or reset to demo mode – all at the developers discretion. This prevents piracy and unauthorised running of the developers’ or integrators’ software. The SX-22 is a full-size, low profile board that plugs directly into a single expansion slot of any iAPX-86-based personal computer. Installation and hardware configuration are claimed to be easy. Software supports direct-to-disk recording and playback with selectable interrupts and input-output addresses. The TMS320C31 floating point signal processor runs at 50NSec with programmable sample rates from 6.25KHz to 50KHz. Frequency response of the SX-22 board is 20Hz to 22KHz + 3 decibels (20KHz maximum with Dolby AC-2) with a range of 92 decibels and a signal-to-noise ratio of 90 decibels minimum throughout the entire range of sampling rates. Total harmonic distortion is 0.005% in both record and playback modes. Antex offers Series 2 software drivers that provides users with access to all of the SX-22’s functions and enables them to do direct-to-disk recording and playback through their own application programs via a series of high-level interface calls. Languages currently supported include C, Pascal, QuickBasic and Assembly. The board is also downward compatible with existing Antex Series 1 drivers. The SX-22 is the seventh product offered in the Antex Series 2 catalogue. The board is available now at $2,300.
