How did Chet get this sound

[amdyck]

I wish I could include the recordings for a better demonstration here. The tune I have in mind is "Siboney" (from 'The Other Chet Atkins). Chet gets a nice deep sound. He gets the same effect with his first recording of Vincent. Both of these tunes are done on the classic guitar. I have finally nailed both of these tunes and would be most happy to learn how he did it. Does anybody know what equipment he was using at the time of the recording ?