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transformer output

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Could you please form a complete sentence?
 
ok wow so you come on this topic to tell me to form a complete sentence and when i do you dont even help me. ive noticed this happen alot on this forum
 
It's been FOUR minutes since your post.... 24-48 hours is typical to wait for a responce, this is not a chat room, though there is a chat room feature.
 
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it doesn't matter how you hook up the transformer output as it is a.c. at that point. Once you add the diode and capacitor it becomes d.c. and as such is polarity sensitive.
 
The output of a transformer does not have a positive or negative. If you connect one end to say the earth of your house, or any "earth point" the other end will go high (say 12v high) for 1/100th of a second and then low (minus 12v ) for about 1/100th second. It doesn't go instantly high and low but takes the shape of a sinewave.
This is called an AC waveform.
Now, ask another question.
 
Check please.
 
Why did you make another thread about your simple amplifier problem?

The TDA2005 amplifiers need a DC power supply, not an AC transformer that is only one part of a DC power supply. AC will destroy the amplifier ICs.
Maybe you have an AC to DC adapter that we call a "wall-wart" because almost every little electronic gaget uses one that plugs into a wall electrical receptacle and hangs there like a wart. But I have never seen a wall-wart with an output power as high as 22W.

An AC to DC adapter has a sketch of its plug printed on it showing which wire is positive and which wire is negative. You can use a multimeter (some cost only $10.00) to measure which wire is which.
 
wow that is actually pretty cool now how does a diode and capacitor turn it into DC?

The diode acts as a one way switch, if you recall what colin55 said --> if you connect one side of the transformers leads to house ground, then on the other wire the signal will swing high above house ground and then swing low below house ground...the diode acts as a one way valve allowing only the negative swing through when the cathode of the diode is connected to the transformer output -OR- the positive swing goes through when the anode is connected to the transformer output. The capacitor serves to flatten out the ripple on the DC output. The capacitor will also need to be connected in accordance with the polarity of the output. If you hooked the cathode of the diode up to the transformer, the output is negative and the capacitor will be hooked up at this point with the negative of the capacitor to the dc output and the positive to the house ground. If the anode is hooked up to the transformer output then the capacitor will be hooked up to the dc output with the positive of the capacitor to the dc output and the negative to the house ground.
 
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