The Sonos / MBL4 are a series of programs that turn a PC with a sound card into an audio compressor/limiter suitable for radio broadcast use.The only drawback is the delay introduced by the computer between input and output.This precludes off air monitoring but as digital transmission systems become widespread with their encoding/decoding delays the delay of the computer is no longer the limiting factor.With the professional 192kHz sound cards now available it is possible to implement stereo multiplex generators and RDS/RBDS encoders in software thus saving on hardware costs.
A demo version of Sonos III is available for download.This version of the software is somewhat restricted in its functionality but does allow the playing of sound files through the processors to a sound card.
Sonos III is the most recent program and is being actively developed.Sonos II / Sonos I / MBL4 are legacy programs that are no longer being developed.The internet stream receiver program RX is also not being developed further since most of its functionality is available in Sonos III.