This Philips/Marantz DPM-7 Digital Processig pre-main amplifier prototype is one of the approx 60 units which Philips handbuilt in Eindhoven, The Netherlands, in the early eighties. The DPM-7 was a showcase of what Philips could do in the beginning of the eighties. Developed by the same group who were responsible for the development of the Philips MFB speakers and lateron the Philips DSS Digital Speakers.
Marantz was not interested, however. They wanted to produce amplifiers with so-called 'pure' sound, even tone controls were a violation of this purism.
From the (conceptual) manual
"The Marantz DPM-7 is an pre-main amplifier comprised of both a digital control amplifier and a 100W x2 high power amplifier. The digitalized control amplifier portion includes the world's first ASP (audio signal processor) developed exclusively for audio equipment. The functions of the control amplifier are processed digitally, thus totally eliminating any chance for diminished sound quality."
Digital sound processing
"Furthermore, the digital sound processing concept has been incorporated in every aspect of the control functions. The DPM-7 is equipped for a great variety of functions, including digital reverberation, a digital graphic equalizer, and many controls for creating the perfect sound field."