I wouldn't try to put a band-aid on the system to try to "cover up" the poor sound of one of your components.
While I'm not an expert on the sound of various models of moderately-priced CD players, I suggest you go out and listen to same and consider making a replacement of that part of your system.
Certainly nothing wrong with tubed electronics in their own right. I've got some myself. But I've also been guilty of trying to use gear and cable as a "tone control," which can get very risky and expensive. Sometimes it works (it did for me), but when it doesn't, you can get involved in the endless cycle of buying and selling equipment.
I'd go directly to the source of the problem and deal with the CD player.
While I'm not an expert on the sound of various models of moderately-priced CD players, I suggest you go out and listen to same and consider making a replacement of that part of your system.
Certainly nothing wrong with tubed electronics in their own right. I've got some myself. But I've also been guilty of trying to use gear and cable as a "tone control," which can get very risky and expensive. Sometimes it works (it did for me), but when it doesn't, you can get involved in the endless cycle of buying and selling equipment.
I'd go directly to the source of the problem and deal with the CD player.