There are two possible causes.
1. Is an analog player with a built-in phono equalizer connected? Connect analog players with built-in phono equalizers to the [CD] terminals.
Also, if the analog player with a built-in phono equalizer has a [PHONO/LINE] selector switch, switch it to [PHONO].
2. Is a USB sound card (audio interface) for a computer connected between the analog player and this unit? If the output of the computer’s audio interface is line level, connect to the [CD] terminals. Also, if the analog player has a [PHONO/LINE] selector switch, switch it to [PHONO].