Audio Hum

[analogue]

I have a Cambridge Audio AXC25 CD player and a Hotel RA-310 amplifier.
When I connect the CD player to any of the line inputs, of the Rotel amplifier, I get a large hum.
I know this is an old amplifier, made before the advent of CD players, but I can not believe that it will not work on any of its inputs.
I am desperate to cure this problem so I can listen to my music collection.

 

[Gray]

...I get a large hum.

Turn the volume to minimum before any further testing as there is a risk of speaker damage from a large hum.
(If the hum doesn't go with the volume at minimum - STOP THE TESTS).

I know this is an old amplifier

It is.
So the obvious question - have you heard it working normally?

I am desperate to cure this problem so I can listen to my music collection.

No rush. As always, a logical process of elimination will identify the cause.

Confirm that the hum level changes with the volume control.
Is the hum there with nothing plugged into any amp input?
If so, the amp needs attention.
If not, see if the twin RCA interconnect cable is the issue - try a different one between CDP and amp.
If there's still a hum, is it on one channel only?
If it is, swap the L & R RCA plugs.
If the hum changes channels, the CDP is the hummer (very unlikely).
If the hum doesn't change channels, the amp has a problem on one side (more likely).
Most likely there's a hum from both sides - and the amp needs help.
See how you get on....