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Cmoy Capacitor help

post #1 of 9
12/9/09 at 3:18am
Thread Starter 
i bought all the parts listed on the tangetsoft website from digikey and the C2 capictors "0.1 µF polypropylene film cap" look nothing like what the example has posted in pictures, But the real trouble is trying to figure out which side is the positive(+) and which is the (-) the leads look exactly the same in length, is there any way to tell which side is which....using the side with writing on the front for reference what corresponds with the left and right legs?

{PS: also if anyone knows how to hook up the toggle switch that would be great too. i have a 2 position switch with 3 connections on the back. i heard to put the (+) in the middle and the (-) on the side that i want to be the on direction?}

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post #2 of 9
12/9/09 at 3:29am
1) Poly film caps are not polarized, you can install them any "direction" you wish.
2) Skip them. Unless your source outputs DC, which most do not, they are not necessary in the CMOY amplifier. Just stick a 1K resistor in their place and enjoy MUCH cleaner sound.
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post #3 of 9
12/9/09 at 3:30am
EDIT: Devil beat me to it.
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post #4 of 9
12/9/09 at 3:54am
Thread Starter 
Quote:
Originally Posted by FallenAngel View Post
1) Poly film caps are not polarized, you can install them any "direction" you wish.
2) Skip them. Unless your source outputs DC, which most do not, they are not necessary in the CMOY amplifier. Just stick a 1K resistor in their place and enjoy MUCH cleaner sound.



so have 3 rows of resistors? is what you suggestiong, what kind of sources output DC? the ipod & mp3 players dont output DC with the 3.5mm jack?
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post #5 of 9
12/9/09 at 3:59am
Quote:
{PS: also if anyone knows how to hook up the toggle switch that would be great too. i have a 2 position switch with 3 connections on the back. i heard to put the (+) in the middle and the (-) on the side that i want to be the on direction?}
They are usually reversed, when the toggle is in the up posistion the bottom terminal is connected to the center terminal but I would suggest checking it with your meter.

And.. I would connect the wires the other way around (the battery positive side to the "bottom" terminal and the amp to the "center" terminal).
That way the unused terminal does not have any voltage running to it when the switch is in the off position.
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post #6 of 9
12/9/09 at 4:06am
Quote:
what kind of sources output DC? the ipod & mp3 players dont output DC with the 3.5mm jack?

Input Capacitors for Headphone Amps

Relevant section from the link above:

Quote:
Since one never knows how much DC offset the various sources out there will have, a conservative design choice is to add a capacitor in series with the input. A capacitor will strip the DC offset from an AC signal in this orientation.

If adding a capacitor fixes the problem, why not always use an input capacitor? That’s the subject of the remainder of this article.
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post #7 of 9
12/9/09 at 4:37am
Thread Starter 


so this build example also seems to be missing the r5 resistor from the diagram above. Can i ask why? Also somthing else i question whether to add when building my amp. Im not sure about a DC source so for now i will add the capictors to be safe. my source sometimes may be from a computer sound card as well.
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post #8 of 9
12/9/09 at 11:44am
Most people do not need R5 and therefore jumper it as is shown in the pic. If you do put a resistor here, it must be a low value (47 ohms). You need either a jumper or a resistor here as this completes the feedback loop.
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post #9 of 9
12/10/09 at 5:58am
film caps are not polarized, therefore you can just put them without worrying of polarity reversal.

as how to wire the "3-connection switch with 2 positions" (or commonly called Single Pole Double Throw / SPDT), you can pretty much wire it like this:
board (+) -> switch's middle connection
battery (+) -> switch's outermost connection (both will do fine, just pick one)
board (-) directly to battery (-)

hope that helps
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