As I understand it, you need to get the analog audio TV output into your preamp with the best quality audio possible.
As was stated by Rbrowne above, I also take the RCA output from my cable box to my Ayre integrated amplifier. I use an HDMI cable from my cable box to my TV for video.
My Wave Broadband/TiVO cable box has a setting used to output the audio to the RCA jacks and NOT the HDMI cable. This means the HDMI cable carries the video to the TV and the cable box outputs the audio to my amplifier (in your case, a pre-amp).
What cable box are you using? Does it have RCA output jacks? If yes, I suggest you take the audio output from your cable box direct to your pre-ampliifier. Please check the audio output setting on your cable box to enable the capability. Does this solve the problem?
As was stated by Rbrowne above, I also take the RCA output from my cable box to my Ayre integrated amplifier. I use an HDMI cable from my cable box to my TV for video.
My Wave Broadband/TiVO cable box has a setting used to output the audio to the RCA jacks and NOT the HDMI cable. This means the HDMI cable carries the video to the TV and the cable box outputs the audio to my amplifier (in your case, a pre-amp).
What cable box are you using? Does it have RCA output jacks? If yes, I suggest you take the audio output from your cable box direct to your pre-ampliifier. Please check the audio output setting on your cable box to enable the capability. Does this solve the problem?