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capacitors Answered

I recently took apart an old stereo reciever that didnt work anymore. As always, I salvaged as much stuff as I could, and came across 2 huge capacitors. They are each about the size of a C- batery,and are rated at 50v, 6800 uF. I, of course, saved them, but now I cant think of anything to do with them!if anyone has any ideas, please let me know stat.


they give nice bright sparks when discharged (although it does not look like a high volt arc)

they can power a led thru resistor and maybe for quite long time

they are good for amateur audio stuff as dc blocker (higher capacity = lower distortion)

alrite... how would i do that thing with the dc blocker? are there any 'ibles on it because i dont have time to check right now

inside many amplifiers there is capacitor in series with the speaker output. this capacitor is the dc blocker it is intended to prevent dc current from running to the speaker - which is wasted as heat in amplifier and speaker and adds nothing to sound output this component is built into the amplifier and you dont need to add one externally some amplifiers dont need dc blocker at all (they output normal ac wave which does not contain dc)

wait, i don't get this whole dc blocker thing, were in the system would it go? i thought that it goes right after the rectifier bridge to balance out the AC converted to DC, which keeps the humm out of a system

there are 2 common uses for big capacitor which i know filtering capacitor for dc after 4 diodes (connected in parallel to dc) - what you said dc blocker in audio circuit (connected in series to speaker) or other circuits with similar problem sound signal is ac in its nature. but many amplifiers can output only varying positive voltage (a wave which is entirely positive - its kinda sum of ac and dc) when sum of ac and dc enters a speaker the ac part goes to sound generation and losses and the dc part to losses (heat) only when we connect a capacitor it blocks dc (after it charged a bit) and allows ac to pass. this way only ac gets to the speaker and it works more efficiently why ? imagine a speaker rated for 10 W. if we give it more power it'll overheat. if we give it mixed ac + dc then both parts together are limited to 10 W but only the ac part is useful. if we block dc then we can give it 10 W of only ac and get higher sound volume for the same 10 W why big capacitor ? actually the capacitor blocks some of the ac too. and it blocks bass more than treble - so it feels like treble boost. the larger the capacitor is - the less ac it blocks (in all frequencies) and the treble boost effect is less noticable

but the capacitor has to be non-polarized to be connected to the speaker, right?

our problem (that we have dc) came from that the amplifier cant output negative voltage but this means as well that the capacitor cant get negative voltage ! :) it sees one polarity all the time ! - yep we can use electrolytic capacitor when capacitor on the + side of speaker : the + is to the amplifier (battery +) and - is to the speaker (series load). just like in any dc circuit

so if an amp can't supply AC voltage, then it's not even an amp i have a really high quality amp, i was thinking of maybe doing this...

some amps (like most single-chip amps) cant output clean ac. they output only mixed ac and dc. but they are still amps. if you connect a speaker you get normal sound as with any true ac amp when dc blocker is needed it is allways built into the amplifier. you dont need to add one externally you need one if you build an amplifier yourself (which is quite simple when you use all-in-one amplifier chips - only few external capacitors and resistors are needed)

cool. do they sell these all in one amplifier chips at like radioshack, or would I need to go to all electronics or something?

i think yes there may also be kits with the amplifier chip and a ready for slodering pcb to build the circuit on many medium quality amplifiers of up to few tens watts use them. you can get 'em from trashed car radios etc

yeh chuck em and take the ones out of a disposable or if your lucky like me a 420 cap lol for a generator