What is a hybrid SA-CD?
A hybrid SA-CD is an SA-CD disc that can be played on regular CD players. The sound quality in that case will, in principle, not be better than that of a regular CD (though the CD-compatible layer is usually derived from the high resolution signal with SBM for better sound … or similar words). The obvious benefit of a hybrid disc is that you don’t need to replace all your CD players by SA-CD players at once. In fact you could even start collecting SA-CDs before you own an SA-CD player. Hybrid SA-CD works in a different way. Both the CD layer and the high-density layer are ‘read’ from the same side. The other side has a printed label, so it is easy to recognize the disc and place it correctly in the tray of the CD player. How it works? The high-density layer is partly reflective, partly transparent. At the wavelength used by regular CD layers (780 nm) the SA-CD layer is invisible so a CD player will just ‘see’ the CD layer. At the wavelength used for DVD and SA-CD (650 nm), the SA-CD la
