Orban’s all-digital OPTIMOD-FM 2300 Audio Processor can help you achieve excellent audio quality in FM stereo broadcasting. Because all processing is performed by high-speed mathematical calculations within Motorola DSP56362 Digital Signal Processing chips, the processing has cleanliness, quality, and stability over time and temperature that is unmatched by analog processors. Starting with V2.0 software, the 2300 can be used as an extremely high-quality stand-alone stereo encoder operating at 64 kHz to 512 kHz sample rates and offering lowpass filtering, overshoot limiting, composite limiting, and an ITU412 multiplex power controller. When used in this mode, the 2300 must be driven (usually via an STL) by a fullfeatured FM audio processor (like Orban’s 8500) that incorporates preemphasis-aware HF limiting and peak control. OPTIMOD-FM 2300 is descended from the industry-standard OPTIMOD-FM audio processors. Thousands of these processors are on the air all over the world. They have proven that the “OPTIMOD sound” attracts and keeps an audience even in the most competitive commercial environment. Because OPTIMOD-FM incorporates several audio processing innovations exclusive to Orban products, you should not assume that it can be operated in the same way as less sophisticated processors. If you do, you may get disappointing results. Take a little time now to familiarize yourself with OPTIMOD-FM. A small investment of your time now will yield large dividends in audio quality. The rest of Section 1 explains how OPTIMOD-FM fits into the FM broadcast facility. Section 2 explains how to install it and set it up. Section 3 tells how to operate OPTIMOD-FM. Sections 4 through 6 provide reference information. OPTIMOD-FM was designed to deliver a high quality sound while simultaneously increasing the average modulation of the channel substantially beyond that achievable by “recording studio”-style compressors and limiters. Because such processing can exaggerate flaws in the source material, it is very important that the source audio be as clean as possible. For best results, feed OPTIMOD-FM unprocessed audio. No other audio process- ing is necessary or desirable. If you wish to place level protection prior to your studio/transmitter link (STL), use an Orban studio level control system expressly designed for this purpose. (At the time of this writing, this is the Orban 8200ST OPTIMOD-Studio Compressor / Limiter / HF Limiter / Clipper.) The 8200ST can be adjusted so that it substitutes for the broadband AGC circuitry in OPTIMOD-FM, which is then defeated.