Question about Yamaha A-S301

This is possible without any problems; RCA (Cinch) inputs are available. For optimal quality, it is also recommended to connect a PC via digital (optical or coaxial) input.

With the DAP version, the signal goes a long way:
Source -> headphone amplifier DAP -> cable -> line input -> amplifier A-S301 -> cable -> loudspeaker

Digital:
Source -> Amplifier A-S301 -> Cable -> Loudspeaker

this should be possible without any problems. the amplifier has 5 RCA line inputs (line 1-3, cd and tuner).