Direct Metal Mastering (DMM) is an analogue mastering technique developed in the 80's by two German companies, Teldec (Telefunken-Decca) and Georg Neumann GmbH. Neumann was responsible for the manufacturing of all DMM cutting equipment as well as supplying complete mastering systems until the 90's when the company was no longer active in the record pressing industry. GZ, formally known as Gramofonove Zavody, implemented Direct Metal Mastering in 1985 and shortly afterwards, it become most used mastering technology in GZ. After introducing the new Vinyl Visual Mastering system in 2010, a new era of further development opportunities and improvements of the DMM cutting process began.
The audio signal coming from the mastering workstation or from a tape is transcribed into a metal master plate through a dedicated DMM cutting head. All modern stereo cutting heads are comprised of two moving coils perpendicular to each other - one for the left and one for the right channel. Movements of both coils are transfered to a cutting stylus with a sharp triangular tip on the end. In the case of DMM, this stylus is specialy made out of grinded diamond and cuts a spiral V-shaped sound groove directly into a high purity copper layer plated on a non-magnetic flat steel substrate. Stampers for record pressing are manufactured directly from such mastered copper plates by a single step electroforming process in electrolytic baths.
GZ Vinyl is the only place in the entire world operating 3 DMM lathes for production of vinyl records: