Cardiac ablation system

An ablation system includes a catheter adapted to be inserted into the heart of a patient. The catheter has a distal end and a plurality of electrodes disposed adjacent the distal end. One of the electrodes being an ablation electrode. An ablation RF energy source connected to the ablation electrode, a patient interface is connected to at least some of the electrodes for acquiring intracardiac ECG signals and a stimulator is connected to the catheter for providing pacing signals thereto. A phase balanced all pass filter is connected between the catheter and the patient interface for suppressing the interference to the intracardiac ECG signals by the RF ablation energy signal.