When I switch between two channels with differing sound formats (e.g. DD to DS) I get a click across my speakers. I'm running a 4m optical cable from Sky+ to my AV amp. It's not the earth (had that checked), it could be the power cables interfering (going to try some trunking) or could it be the delay whilst the Sky+ box thinks about what sound format to use ? Incidentally it doesn't happen when switching between sources (e.g. Sky+ to SACD) so I'm sceptical it's the amp having a problem. All suggestions welcomed !