You probably have mixed up the 2 red RCA cables:
- 1 red RCA is a part of the video component cable and is dedicated to the video signal
- the other red RCA is a part of the analog stereo audio signal (right side)
If you mix up those 2 physically identical cables, you will :
- loose the right side audio channel (which gives you this impression of bad quality sound)
- loose the red color in the RGB mix of the video signal
Therefore, just switch those 2 cables (the picture and sound will be back to optimal quality)