[MrFixr55]

I'm a little surprised that you do not get full volume from the CD player.  If you put the input jack just before the volume control, there should be plenty of gain for a "line level" input.  Are you using a CD Deck or the headphone output of a portable CD Player?  If you have access to a component preamp, this may be useful. A "Mono" cord? If the 3.5mm plug is only "TS" (tip and shank or tip and shield, then this type of cable will short one channel out. This may lower the sound and damage the CFD Player. Either of the 2 diagrams (placed there while I took a break from typing this) will work. The second one is easier and cheaper to build. In the diagram that uses resistors, values for RMix 1 and RMix 2 of 75-150 Ohm will suffice.

I did this to a Crosley 02CA.  The Customer liked to play jazz guitar and liked the sound.  Of course, he also used this as a radio.  Yes, granted that he could not duplicate Jimi Hendrix or (Lord help us) Led Zeppelin.  The "mod" done to this unit was to make it like the similar 02CQ which had a switchable phono input.  The input was put between the detector and volume control.

I don't have a great home transmitter.  I have a Talking House transmitter and a Vectronics Kit transmitter.  I don't expect full HiFi but I have never been as impressed with AM reception from these transmitters as I have been with direct connect.  My guess is that the relatively low Broadcast frequency, the low IF frequency and the distortion of a detector subtract from signal quality.