The Stereo 25, a pre-amplifier from 1966, was the first relevant product from Sinclair in the hi-fi market area. It was sold already assembled, distancing itself from the tradition at the time, when products were sold in kits. It connected to the PZ 3 (power supply) and to the Z12 amplifier and, together, they created the basis for an at-home hi-fi system. It was later replaced by the Stereo 60.