sunnysal Posted February 9, 2003 Share Posted February 9, 2003 I found an articel thats mentions the use of a 3mf capacitor. I know what a 3uf would be and a 3pf...but what do they mean by 3mf???? would that be 3000uf??? this is for a LC filter for my xover....second question...I want to use as many parts as I can form existing things I have laying around, is it ridiculous to "make" a 13uf cap by binding together a 5uf a 6.2uf and two 1uf caps in paralell? is that really dumb? third and last question? is close enough good enough? since many caps are spec´d 10% can I use a 2.2uf if a 2uf is spec´d? thanks for the help guys, tony Quote Link to comment Share on other sites More sharing options...
minn_male42 Posted February 9, 2003 Share Posted February 9, 2003 3mf is the same as 3uf... as for the 10% rating....it means plus or minus 10% of the rated value....so a 3mf cap will vary from 2.7mf to 3.3mf russ Quote Link to comment Share on other sites More sharing options...
Malcolm Posted February 9, 2003 Share Posted February 9, 2003 MF is the abbreviation for millifarad, 1/1000 of a farad. But some folks seem to use it instead of uF for microfarad, which is 1/1000000 of a farad. There is also nF for nanofarad, which is 1/1000000000 of a farard. And ofcourse, pF stands for 1/1000000000000 of a farad. No, it is not ridiculous to make a 13 uF cap by paralleling parts. It doesn't make economic sense for a manufacturer. It is cheaper to buy the right part than combine parts. But when you are playing with parts out of your junk box it makes sense. Best to use similar parts when doing it, e.g. all metallized polypropylene, all electrolytic, etc. Yes, close is usually good enough. Most of the time you can replace a 2 uF cap with a 2.2 uF cap. There are critical circuits, though, where this much of a difference could cause the circuit to work other than as desired, or to not work at all. Quote Link to comment Share on other sites More sharing options...
JohnA Posted February 10, 2003 Share Posted February 10, 2003 Tony, The higher the "order" of the filter the more important the actual value of the component becomes. For a 1st order tweeter filter, I've found most anything from 2 to 3.3 is acceptable. Part of it is how close to "theory" do you want to stay, but the practical side says with varying impedance vs frequency, quite a bit of leeway is present. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted February 10, 2003 Author Share Posted February 10, 2003 thanks guys, now I am adding a diagram that shows basically a type A x-over with a LC filter for cutting 9k to the mid (I think! lol!) and a zobel for the tweet and mid section. anyone who could comment would be of great assistance to me, I had the ole electronics text book out all weekend trying to verify values for this, one of my doubts is if I should be taking the LC filter to ground (like the zobel) or leave it in-line to the mid like I do...thanks tony Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 10, 2003 Share Posted February 10, 2003 Tony, The R-C network you have connected across the input on your schematic is a Zobel for the woofer and therefore should be connected across the woofer. I would not bother with it if I were you. Leave it out! The other parts in the squawker is a "P trap". It kills 9 Khz. That is a good idea if you have the older K55-V squawker with the push-pin spring-loaded connections. If you have the later K55v with solder connections or the K55M you don't need it. BTW - Paralleling up smaller values of caps to get a large value is a good thing. It will make a cap with lower loss than one big one. Al K. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted February 10, 2003 Author Share Posted February 10, 2003 thanks Al, so I pretty much would have a type A left after removing those. I will not make any changes until I get my new SET amp and see how it sounds with the ALK unit. the benefit of very flat impedance response that your x-over presents should be a great advantage with the SET, no? the type A would probably be better for my Dynaco or SS amp. tony Quote Link to comment Share on other sites More sharing options...
johnnyp Posted February 10, 2003 Share Posted February 10, 2003 Although one can parallel multiple capacitors to achieve a desired capacitance sum, I have found that I definitely do not like the sound of more than two caps in parallel. Can't explain why. YMMV. I have currently altered my Model AA to use a single 2uF cap on the tweeter. This is much more pleasant to my ears than the stock 3rd order filter. I realize that I risk frying my T-35s. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted February 11, 2003 Share Posted February 11, 2003 John, If you don't like the sound of several cap in parallel it means you would probably like old paper-in-oil caps. This is becasue paralleling caps reduces loss and increases the highs that get through. High loss caps kill highs making a more "mellow" sound. Tony, Yes, what you will have left is the "A" nectork without the misplaced Zobel and the P-trap. Personally, I think constant impedance is an advantage for any amp, but I'm sure some need it more than others. Al K. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted February 11, 2003 Author Share Posted February 11, 2003 Thanks Al, I am sure that a 2A3 SET will thank me for constant impedance...I will let you know how everything sounds once Jean Francios sedns my the monoblocks. regards, tony btw do you still have the impedance measurement curves for the alk x-overs? I would love to see them, thanks, tony Quote Link to comment Share on other sites More sharing options...
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