interconnect for CAL delta/alpha pair

I recently purchased a CAL Alpha and delta and was wondering which input to use the AT&T,Optical,coaxial 75 ohm or balanced 110 ohm Also what brand is recomended in the under $100 range.
I had the same digital front end before I upgraded to Classe. I would use the balanced or the AT&T and avoid the optical. I used both in my system. A excellent AT&T cable was the PS Audio and a good balanced cable match was Tara Labs. You should be able to find a used Tara in your price range, the AT&T may be harder to find used. Try Paul at the Cable Company 1-800-328-9973. He is always a good resource. Good luck.
I absolutely agree. I had a Delta/Alpha combination and found the AT&T and balanced connections were best. The AT&T gave a smoother presentation than the balanced and therefore was preferred (due to my Thiel 3.6 speakers working better with a smooth front end), but in other systems I know others were very happy with the balanced. But your budget is probably the clincher - you are more likely to find something like an Audioquest Optilink Pro AT&T connection second-hand for this price than you are to find a balanced digital cable that is in the same league. At around $150 second-hand you can get some very good cables - Illuminations Orchid, Audioquest Digital 2, Audioquest Falcon, Madrigal (sorry but forgot yhe model number), etc.
I had Altis Altimate optical, and when my system got better I realized that AES/EBU or S/PDIF were both better. I had a good AES/EBU with van den Hul silver 110 ohm wire, but when I changed to Stealth I got much better sound, and it comes with a money-back guarantee. See