There are two possible causes.
1. Is an analog player with an internal phono equalizer connected?
When using an analog player with an internal phono equalizer, connect it to the [CD/LINE] terminals. Or, if the analog player with internal phono equalizer is equipped with a PHONO/LINE selector switch, switch it to PHONO.
2. Is a computer sound card (audio interface) connected between the analog player and this unit?
If the computer sound card's output has a line level, connect to the [CD/LINE] terminals. Or, if the analog player is equipped with a PHONO/LINE selector switch, switch it to PHONO.