To use a (PC/CPC Plus-style) DB-25 printer cable on a classic CPC, an adapter is needed. This adapter can be build using a female DB-25 socket and an edge connector (or a male Centronics plug for the german Schneider CPC). Using ribbon cable crimp connectors is the easiest way. Just connect each plug to the ribbon cable and pay attention that you always connect the red wire to pin 1 of the connector. Then cut pin 16 (which is the printer reset pin) using a sharp knife.