Have a question about CD players. I have 2 changers, an Onkyo 6 disc and a Harmon Kardon 5 disc. I took both apart to clean pick up and found they both use the same laser pick up. I have them connected to my pre pro via coax digital connection. The Onkyo has a noticeably louder output than the HK. This is using the same coax cable. What else in the player is utilized other than the pick up if I’m using the D/A in the pre pro?