Pioneer introduced a line of true audiophile  components in the late 1970s known as Series 20.  These components used the latest engineering and displayed the finest quality parts Pioneer had ever manufactured.   The components included the C-21 Preamplifier, the M-22 and M-25 Amplifier, the D-23 Crossover, the F-26 and F-28 tuner, the A-27 Integrated Amplifier, the PLC-590 Turntable and PA-1000 Tonearm.  There was also a U-24 Program Selector used primarily by Pioneer dealers.  All but the turntable and tonearm are covered in this section.