• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Mains filter capacitors

What's the general consensus on using mains filter capacitors (class X and class Y) between live and neutral, live and safety ground, and neutral and safety ground? I remember reading somewhere that this can cause more noise problems than it helps.
 
Mains filter capacitors are useful to keep interference from switch mode power supplies getting back into the mains.
Class X2 between Live and Neutral with Class Y between Live and Earth along with Neutral and Earth.
They can also reduce mains borne interference by shunting RF noise to ground through the Class Y capacitors.

The Death Cap is a totally different, unsafe method of "Grounding" the chassis of the equipment to either Live or Neutral, in an attempt to remove mains borne RF noise. Very dangerous as if the capacitor fails, you could have a Live chassis!

Class Y fail open circuit by design.

Class X2 are self healing but will fail when totally damaged either open circuit or short circuit but as it is fitted across the Live to Neutral, will only blow your mains fuse.
 

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