You can adjust the expected level of the line-in on the ZP90 (I think, its been a while), have you tried that? A CD player should not need a pre-amp.

No preamp needed in any I have seen, but I had a CDP once that also had a volume level control, probably there to avoid input signal clipping, that may need to be moved around.

Huh. Did that CDP have two outputs, one line level as normal, and a second controlled by the volume control? I think, and it’s been years now, so the memory may not be valid, that the only devices I’ve seen like that had the volume control only affect a headphone jack. 

Nope, it was a Marantz CD 6000 OSE with the volume control on the remote for the analog output socket pair, ranging between 0dB and -30dB. The default level at power turn on was max volume, 0Db.

Wow, interesting. What an unusual setup.

Not that unusual - I had a Quad CDP once as well, that had variable line outputs as well as fixed. Two pair of jacks in that case though. The idea behind the variable outputs was to eliminate the need for the preamp box of the typical pre + power amp two box combination common in audiophile circles. For such deviant audiophiles that could do with a box less:-). 

I’m afraid my audiophile experience was only looking longingly at equipment I couldn’t afford. ;)

Bottom line though is that:

1. I still retained the Quad pre amp to retain my box count back in the day.
2. Today, even if I had the Quad power amp, I would have been very content with just it out of sight with an Echo Show 5 wired to its input jacks.

Which would yield audibly the same results if the speakers are unchanged:-). 

Thanks all