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so i placed a cap array (2uf, .1 and .01uf) across + and neutral, and while it does good things to address the up & down nature of AC quality associated with afternoon summers, it also takes a bit too much off the top end.
is it the larger cap (2uf) that takes the most off the top, or is it the small ones?
I second for RC use. Because of two reasons.
RC filter across + and Neutral slightly improving the upper peak of sinusoidal main voltage. And more importantly, RC filter kills primary resonance of main transformer.
Choice of resistors and capacitors is very important. Resistor should be a carbon composite type (A.Bradley or Stackpole) 330 ohm/1 watt. And best capacitor (to me) is some fim & foil type. I use 15 nF/1.5 KV, ERO KP-1832.
But any value from 10nF-15nF (> 1KV) will be OK.
Just try it. It is not difficult.
First, you need to read the post above about SAFETY FIRST. If you get it, great. If it's too dense for you, then be very careful that you're using X or Y caps rated for the voltage in your country AND be sure you know how to wire these up so as not to create a short.
Second, you should read the posts about AC filtering by Al Sekela on this board. He posted about how to rig up R-C and R-C-R filters for AC current filtering and those are reliable. I do recall that he posted the cap values as well as the resistor values.
If any of this stuff is beyond your full understanding, please don't fool with this kind of tweak! I know I'm sounding like an old fart here, but we don't want people doing things that end up with them being dead.
You should use mains rated MKP capacitors for this purpose.
2 uF is quite a large value for safety reasons and you need to be very careful with choice.
Line-filter capacitors come in two general classes (as defined by the International Electrotechnical Commission (IEC), the international standards organization for electrical and electronics matters) and must be approved by whichever safety agency holds sway where the equipment will be sold. In fact, you can always recognize a line-filter capacitor by the "EN132400" printed on it, plus agency acronyms (UL, VDE, CSA, etc.). Older capacitors would have the symbols for SEMKO, DEMKO, and others, but these no longer exist as governmental agencies and are, if they exist at all, commercial enterprises carrying out testing.
Class X is for applications where failure could not lead to electric shock (hot to neutral). Class X1 capacitors are intended to operate safely even in the presence of spikes on the mains supply of up to 4 kV (installation category 3 or overvoltage category 3 according to IEC60664), which are normally industrial supplies, but some standards call up class X1 capacitors if they are connected directly to the mains supply upstream of the equipment fuse, irrespective of the type of mains supply. Class X2 capacitors are intended to operate safely even in the presence of spikes on the mains supply of up to 2.5 kV (installation category 2 or overvoltage category 2 according to IEC60060), which are normally residential, commercial and light industrial supplies. X capacitors can be found from 0.001 uF to at least 10 uF and are only made in film.
Class Y capacitors are for applications where failure could lead to electric shock if the ground connection were lost. This includes hot/neutral to ground, and antenna isolation capacitors. Because Y capacitors shunt current to ground, leakage-current limitations limit their size to a maximum of about 4700 pF in many commercial and industrial applications (but refer to the relevant standard for definite information) and about 470 pF in medical applications.Cappic Larger ones are available however. Y caps are available from 1000 pF to 0.1 uF and are made in both film and ceramic.
Classes X1, X2, and Y were originally defined by the IEC in IEC 60384-14. CENELEC has adopted EN 132400 (technically equivalent to, but structurally different from IEC 384-14 2nd edition), which now defines seven classes of line-filter capacitors. Class X1 capacitors are impulse tested to 4 kV (higher for capacitors over 1.0 uF). Class X2 capacitors are impulse tested to 2.5 kV (higher for capacitors over 1.0 uF). Class Y1 capacitors are impulse tested to 8 kV, and Class Y2 are impulse tested to 5 kV. Classes X3, Y3, and Y4 are for lower-voltage capacitors, none of which are presently called up in safety standards. Other impulse tests also apply. These include a 1000 hour endurance test during which the capacitor is subjected to a continuous overvoltage condition, plus periodic 1000 VAC spikes, and a flammability test during which the capacitor is hit with a series of transients while under rated voltage. Capacitors conforming to IEC60384-14 normally also conform to EN132400, and vice versa, and should be accepted in all European countries.
Line-filter capacitor voltage ratings are based on what the agency considers the "nominal" line voltage in its jurisdiction to be. A part can have one voltage rating in the US and Canada (125 or 250 VAC), a different rating in Europe (perhaps 275 or 300 VAC), and the manufacturor might recommend its use at a higher voltage yet (a 250 VAC part on a 260 VAC measured line). This can make for a little confusion in application, and it may be best to ask the manufacturor for details.
These capacitors are also rated according to min/max temperature and allowed average annual humidity exposure. IEC 68-1 calls for an X/Y/Z marking system where X is the low-temperature limit, Y is the high-temperature limit, and Z is the number of days tested in a damp heat test (+40C at 93% RH). For example, 40/100/56 would mean the capacitor was rated from -40 to +100C and tested for 56 days in the damp heat test. This is printed on the capacitor.
Hello, I was reading this with interest as I have been using an array of about (5) 25uf Clarity Pollyprop caps in paralell giving me a total of 125uf across the hot and neutral. These are rated at 600 Volts and my AC is 120 volt. This has produced a nice smoothing of the highs and a reduction of "hashy" sounds. They are soldered together and placed in a shoe box then plugged into the wall outlet. It has been like this for years now with no problems. Am I taking a big risk here? Please let me know.
I too am using caps rated for something else, I don't know if these other ratings even existed then. But... They are in a metal outlet box with a metal cover siting on the floor with a heavy braid returning the case to safety ground.
My theory is that there are only two risks, fire and shock. As long as the ground run is good on the outlet there should be no shock risk and it seems likely to me that any failure that draws enough current to heat the outside of the metal box enough to start a fire will also trip the breaker. If that thinking appeals to you, you should have a metal shoebox, or at least a fire retardant one, I would be a little nervous with cardboard...
The main thing about X and Y capacitors besides they are designed to withstand voltage spikes is they must fail without being a fire hazard.
If you are okay with what you have, enjoy.
Personally I will not risk my home and my family's life for some tweak.
"Personally I will not risk my home and my family's life for some tweak."
Thanks for the thought, I agree which is why I'm considering changing them on GP's. Actually I don't even know if the filtering is doing anything beneficial where I'm using it so it may be a mute point.
I'm confident that they aren't a significant fire hazard for the reasons I stated but if they blow it would probably be a stinky mess. I just built the thing as an experiment over 30 years ago and it didn't do much good sonically so I just threw it in the junk box. But when I moved here I needed a short extension cord and it was in the stereo box so...
I appreciate for your concern and will revisit it.
Just what I needed, and I didn't have to even ask...
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