as the signal gets hotter. Together the dynamics processor and time delay create sustained bass frequencies that are perceived as being louder yet do not noticeably increase peak output. Aphex started selling the professional units, and introduced two low-cost models: Type B and Type C. The Aural Exciter circuit is now licensed by several manufacturers. The so-called Big Bottom circuit was added in 1992. Later revisions of the Aphex Aural Exciter included the Model 104 Type C and Type C2 units. The most recent version is the Model EXCITER Aural Exciter and Optical Big Bottom. Functionally similar units from competing manufacturers are generically known either as 'psychoacoustic processors' or more commonly just as 'enhancers'. Broadly comparable products are now available from BBE, Joemeek, SPL, and Behringer, implemented using either analogue or digital hardware, or software. Applications Aphex has also released several audio effects apps that apply the Aphex processing to digital music in iTunes. Licensing Aphex continues to expand its licensing activities and has contracts with a variety of audio, music and other OEMs. References External links Manufacturers of professional audio equipment Audio equipment manufacturers of the United States