This error is generally as a result of the amp seeing DC current from the speakers and going into protection mode to protect itself. This is generally due to the volume being turned up too high, or the speakers are not able to handle the power.

If DIRAC is enabled, turn it off and see if the error occurs - often DIRAC can cause the speakers to be overdriven and thus return DC voltage. If DIRAC disabled solves the problem then the curves need to be turned down. 

Remove any power conditioners.

As a last resort, the protection sensitivity can be turned down to medium. This is done via the engineering menu (press and hold front panel menu button for +5 secs).

4 Ohm Speakers - the Arcam AVRs can go down the 4 Ohm speakers however when trying to achieve extreme high SPL the unit may go into protection and display the Error 1 DC fault. Try setting the front speakers to small and use a subwoofer if high SPLs, e.g. 110-115 dBs are desired, or go up to a higher power. Continued use of a lower powered amp or an amp with lower protection is not recommended.