[kyrill]

hi

the better power bars with line filtering use often noise surpressing filmcaps like for instance the 0.1uF 240V Vishay/Roederstein F1710 Y2 Suppression Capacitors

for some reason even at  the primary side of transformers it is possible to hear the quality of the suppression caps.
but how are the workings of these for instance 0.1uF Vishay noise surpressing filmcaps different than "audio" filmcaps if the voltage is the same too? Can i use a 0.1uF 400V Sonicap fimcap too as a "noise surpression" cap in a powerbar with no danger? If yes there is chance they sound better in power line conditioners or power bars?

[JoshK]

Take a look at the threads in the lab about the Felicia and Felix power conditioner projects.  A lot of info on the appropriateness of caps in power filtering is discussed there and Occam has shared a lot of his knowledge with us.  Basically you need to use a cap that will gaurantee to fail open and not short. A cap when it fails can be dangerous if it doesn't fail open (circuit), or even if it fails quasi open it can be dangerous because of the amount of ground current it might be leaking.  Voltage isn't the only concern unfortunately.

[kyrill]

Good advice Josh
I have read that Felicia thread and the Auricap was suggested as a possible try with yr warning

But
IS there a functional difference between those caps ( official surpression caps) and "normal filmcaps except from open or closed failure's context?
BTW a lot of coupling caps find their way into much higher dangerous ( voltages >300-500V) ground like tube amplifiers and a lot of tube amps have wooden bases 

i know the Amperage in coupling caps is low but suppression caps parallel to the hot AC lead  have very low amperage as well

And the normal household electricity have anti short cut circuits ( dont know the real english word for it)


And for instance  can teflon ( in Teflon filmcaps) fail so that both leads shorcut each other? I have the strange notion that teflon's "half-life" is eternal ehhh in a way 

[Occam]

Caps rated as X1(440vac?), X2(240vac) are specified (and listed) are 'guaranteed'/certified to fail either totally open, taking it out of the circuit, or totally shorted, which would trip a breaker. Because they can fail shorted, they are used across the line, from hot to neutral. These are used to address differential/normal mode noise.

Caps rated as Y1,Y2 are specified .... to fail totally open. This means they may used also from Hot/Neutral to safety ground as they will not nominally put mains voltage to a grounded chassis, even if they fail because they will (hopefully) only fail open. These are used to address common mode noise.

Indeed, the characteristics (frequency vs impedance, etc...) of the cap(s) can be subjectively perceived (I will inevitably  rue this statement). Personally, I only use 'rated' caps for mains use, and think the proper combinations can meet my needs.

Mains X & Y will come in ceramic (inexpensive and mediocre performance) and metalized film (Mylar or Polypropolenne) or metalized paper. I've not found foil caps certified for these uses, I assume because they lack the self healing characteristics of metalized caps.

[kyrill]

thx occam