There are several solutions depending on whether your amplifier is new or old.
Optical cable for amplifier: LogiLink CA Toslink 4.65 Frs from Digitec provided that the amplifier is equipped with Toslink.
Or an HDMI cable type Gembird HDMI (Typ A) - HDMI (Typ A) 4.50 Frs if the amplifier is equipped with HDMI
Otherwise you need an adaptor: LogiLink Coaxial and Toslink adaptor 17.30 Frs from Digitec + a coaxial cable: Goobay Stereo connection cable 2x Cinch 4.95 Frs at Digitec the old amplifier is equipped with two cinches + a Toslink optical cable as above at 4.65 Frs Best regards