Adding to the last poster on the topic of volume controls; unless the CD player has a very high quality analogue stepped antenuator you are better off with direct out to an amp with a passive linestage, or external preamp, with quality stepped antenuators.
Matching the voltage/impedance output to the input of the amplifier is absolutely critical with a passive linestage (or active for that matter)
Matching the voltage/impedance output to the input of the amplifier is absolutely critical with a passive linestage (or active for that matter)