What do you have the impedance set at? It should be 47,000 ohms (that's 47K ohms). If you have it set less than this, than that is the cause of your problem.
If it is set correctly, the problem may be that you are trying to match the gain of your CD player, which is almost always of higher gain than a phono section. This is normal.
If it is set correctly, the problem may be that you are trying to match the gain of your CD player, which is almost always of higher gain than a phono section. This is normal.