I've had channel imbalance issues that I'm trying to ignore and there was a minor hiss that only appeared with the RCAs. It's all gone with the XLRs. Even with the XLRs I can still hear sound when the volume is at 0 but I'm trying to ignore that too. At 10 o'clock they all sound amazing.
probably fault rca cabel.
biggest improvement with xlr is that you get higher threshold and volume