The problem could have several causes. Here are some possible reasons and solutions:

1. low output level of the CD player
The Renkforce CD 1000 may have a very low output level, which means that the amplifier has to be turned up very high.
Solution: If the CD player has a volume control or a level selector switch, check that it is set to the highest level.

2. defective or incorrect cinch cable
If the cable is damaged or of poor quality, the signal may be lost.
Solution: Try a different cinch cable.

3. faulty or incompatible signal levels between CD player and amplifier
The CD inputs should be designed for line level signals (approx. 2V RMS). If the CD player has a lower output level, the volume may be too low.
Solution: Test the CD player on a different amplifier or connect a different source device to the CD input of the Yamaha A-S201 to see if the problem persists.

4) CD player only outputs signal on one channel or with phase problems
If the signal is only output on one channel or with phase cancellation, it may sound very quiet.
Solution: Test the headphone output of the CD player with another device to see if the signal sounds normal.

5. faulty CD player or amplifier input
If the CD player on another amplifier is also quiet, it could be faulty.
If another device sounds normal on the CD input of the Yamaha amplifier, it is probably the CD player.
Solution: Test the device on another amplifier or test another device on the CD input of the Yamaha.

If none of these points help, the CD player or the amplifier may be faulty.