What could this be?

[Dublove]

i got a new head-unit as my old one was swiped last week. BUT when playing cds as i press the fast pedal it causes interference, yet not when playing the radio. Not sure about ipod playback yet as I'm waiting for the ipod adaptor to arrive. As soon as I take my foot off the pedal playback is fine.

Never happened before with the old hu.

Any ideas?

 

[Dup]

Sounds like you've connected your pre-outs while the battery on your amp(s) was connected.

It happened on my headunit. Otherwise you could have a dodgy earthing somewhere.