Radio problem related to battery?

[Decolliber]

I have been having a problem with the volume of my Alpine radio cutting out intermittently after about ten minutes of driving. I assumed it was a wiring problem, but after running the power wires (red & yellow) directly to the battery, and putting some test speakers on the passenger floor, with wires directly to the radio, the problem remained. It also occurs when playing a CD, so its not the antenna.
Now this AM my battery is dead and I replaced it; Sears confirmed that the battery was dead. I am wondering if a dying battery could cause the radio volume to cut out after 10 minutes of driving. My intuition says no, because if the battery is weak enough that it can't manage to power the radio amplifier, it would not have been able to drive the starter motor.
Of course, I can find out now by seeing if the radio problem comes bacck with a new battery, but I am curious as to whether a failing battery can cause a radio problem.
BTW, the battery Sears sold me was $100, and much longer than the old Interstate that was put in by the p/o. The new one fits the tabs on the battery tray, or would fit if the nuts to remove the clamp were not rusted on and unmoveable. The new battery is also 800 CCA. Isn't that rather high? All other car batteries I have seen are around 500CCA.

[Planter91C2]

i think when you are driving the radio cannot drain the battery because the alternator is constantly charging it, and the radio is running off of that electricity. so, i think your intuition is right.