Audio Research CD7 owners help needed

My ARC CD7 is causing cracking distortion noise. That noise is coming only from the left channel with and without audio signal (I mean with and without CD playing when power is on). Can somebody advise me what tube is bad. There are those codes for tube installation, so what tube should I replace first. Thank you.
If you phone Audio Research with a description of the problem they will probably tell you what tube needs replaced and ship it to you. Quite often free of charge because that's the kind of people they are.
Lak is correct. I had the same problem ... the tubes in the stock CD7 "drift" and need replacement. To my surprise, ARC sent the tubes free of charge.

For the best results, send your player back to ARC for the "update." Its free of charge for original owners and the improvement will astound you. As an added bonus ... no more tube drift.