Yes, I just wrote an article about building an A/V adapter for my Admiral 24C15:
http://www.antiqueradio.org/A-V_Adap...VintageTVs.htm
That approach has some pros and cons, as discussed in the article.
The contrast control may affect audio because they're indirectly related through a bias circuit. This paragraph is from the end of the audio description in the Rider's manual:
"A low negative voltage derived from the output damping tube (V23) grid circuit is applied to the contrast control R108A and then to the grids of the i-f amplifier tubes V3 and V12. This is used to change bias on these tubes and therefore the video i-f gain."
The audio is picked off following V3, so the stronger the signal there, the stronger your audio.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html