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Old 30th January 2009, 02:38 AM   #1
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Default Newbie Question about caps....

Question...do Metallized Polypropylene caps have a + and - side?

How about Metal Oxide resistors?

One final one....if there is a +/-, does the - side go to the amp and the + go to the speaker?

Thanks in advance for your help and knowledge, I feel a little stupid asking a question like this, but I figure that it is better to ask then it is to destroy stuff for no reason!!
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Old 30th January 2009, 03:10 AM   #2
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cmon....I'm really excited to try this out, I have the parts and a soldering iron ready to go!!
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Old 30th January 2009, 03:45 AM   #3
alvaius is offline alvaius  Canada
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Certainly no on resistors, and highly unlikely the caps are polarized. It may be best to put the soldering iron away and do a bit of reading. You will get a lot of enjoyment out of the knowledge.
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Old 30th January 2009, 04:06 AM   #4
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Thanks for the reply! I really appreciate the comment about doing research, I really believe that to gain a true understanding that you need to fully appreciate this hobby you need a solid foundation of the mathematics behind the scenes. I am pretty comfortable with the theory, I have a mechanical engineering background, but the practical aspect of this endeavor into speakers has me a little out of my league. I am fairly comfortable soldering, but some of the relatively simple things elude me from lack of exposure/experience.

I have been reading and researching on the net for about the past two or three months before I started to play around my my current speakers. I have three identical speakers, I am systematically making mods to each to determine what changes have what effect on the sound and comparing them one to another. I am very curious as to how the crossover mod will change the sound.
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Old 30th January 2009, 05:03 AM   #5
Dan2 is offline Dan2  South Africa
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think about this - an amp supplies the speaker with an AC signal, so half of the time current is flowing in one direction, and the other half of the time it flows in the other direction. if you are hooking caps up to speakers they should be non-polar.
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Old 2nd February 2009, 11:51 PM   #6
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Intrinsicallically, a film capacitor is symmetrical to what is applied to it.
In a normal, sensible world, all capacitors would be the same, and you would be able to fit them any which way you wanted.
The rat in the ointment is electrolytics, which behave, and are created to behave, quite unusually. This is due to the "dielectric" material being a manufacured oxide layer which exists only on the anode and not the cathode.
So basically, unless it's an electolytic, you can do what you want.
(Except if it's a bipolar electrolytic, in which case............
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Old 3rd February 2009, 02:50 AM   #7
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Do not put away your soldering iron.
But DO the research as well.

Just be careful when turning it on for the first time. Always use a fuse on the AC power cord.
What I used to do, is place a glass bowl over the circuit, fire it up, and if you've done your research...there won't actually be any fire.

=R=
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Old 3rd February 2009, 03:15 PM   #8
jitter is offline jitter  Netherlands
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Quote:
Originally posted by MCampbell
So basically, unless it's an electolytic, you can do what you want.
(Except if it's a bipolar electrolytic, in which case............
Don't forget tantalum capacitors, they too have a polarity that needs to be observed. Note the difference in markings: on electrolytics it's usually the minus that's marked, on tantalums the plus.
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Old 3rd February 2009, 03:23 PM   #9
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So that's why half my tantalums keep blowing up ;-)
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Old 3rd February 2009, 08:13 PM   #10
jitter is offline jitter  Netherlands
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Funny thing is I've come across incorrectly placed tantalums that worked for a while before they blew. Some blow straight away, others survive many hours!
A colleague always warns us when he starts testing boards with a lot of SMD tantalum capacitors. Why? Since RoHS there are some that blow spontaneously at first power up, depsite being placed correctly and NOT being overvolted!
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