I have a pair of Magnepan MMG's connected to two Emotiva mono blocks and a Emotiva preamp. I stream music from Spotify on my iPad and send it to the preamp with an Apple Airport Express which is connected to the preamp with an optical cable.

My problem is this, when I select a song to play the speakers give out a loud cracking noise before the song starts playing. There is no further cracking noise as the playlist proceeds. If however I choose another song then the loud crack sounds before the song starts.

Even if I turn the sound completely down the speakers make the cracking noise.

Does anyone know a solution for this problem?

Thanks