I am not familiar with the Denon turntable you are using, however, if it does have a built in phono stage, check to see if there is a gain setting, low/high or a DB setting for the gain, in which case you may want to set higher, or, even a boost switch. The gain switch might be labeled with a DB value, perhaps 35,40,45, 50, 55, 65, I really do not know, but you might want to use a higher setting to see if that helps. If you are still hearing noise from the speakers but at a low volume, check the wires on the back of the turntable to see if they are securely plugged in all of the way, also check the headshell wires. Also, not being familiar with the NAD you are using, make sure to check that if an individual setting for each source is not set too low, on many home theater receivers, the volume for each source can be manually set, therefore meaning a source could potentially not be sourced matched with the rest of the components in terms of volume.
Ciao,
Audioquest4life
Ciao,
Audioquest4life