Do you connect the output from turntable into the PHONO connection on the amplifier?
Because the turbtable only send the low and weak signal (maybe 2.2mV for MM or even lower as around 0.4 mv For MC head), so if you connect to CD or AUX port on the back of amplifier, you won't hear enough sound. [br]
If you don't have PHONO input, then you should find a PHONO amplifing machine in between the two machines, which can be found in fairly low price about under 100 bucks for low grade types. [br]
If you already used the phono port, then you should check if the turntable get some issues to send the signal.