DC offset

[whiz115]

A speaker uses an AC signal that keeps changing its polarity. If a polarized capacitor is used in a speaker's crossover network then the reversed polarity of the signal for half of each cycle would ruin it. So NP (non-polarized) capacitors are used.

i was afraid that this is the answer..i'm saying that because it is confusing! from the above posts i understood that a capacitor removes DC offset (centers waveform to 0V) so the signal swings positive (as before..) and now it's able to swing to negative...

when we connect two devices together and their inputs/outputs have capling capacitors the device that accepts the input signal should have problem because most of the time...these capacitors are polarized.

 

[audioguru]

In the preamp circuit, C1 is only 0.22uF and its polarity could be either way depending on the current of the microphone. So don't use a polarized electrolytic capacitor, use a non-polar metalized-poly capacitor instead.

C2 in the preamp circuit always has the same polarity so it is fine. The output capacitor's polarity might be reversed so use a non-polarized electrolytic capacitor for it. Digikey sells millions of them.

 

[whiz115]

The output capacitor's polarity might be reversed so use a non-polarized electrolytic capacitor for it. Digikey sells millions of them.

from what i understand the output capacitor of the preamp is ok to be polarized because the signal has DC offset...and there isn't negative voltage...but after the output capacitor the signal is centered to 0V (no DC offset).
If next stage that follows after the preamp has polarized capacitor in the input, does it cause problem?

 

[audioguru]

If next stage that follows after the preamp has polarized capacitor in the input, does it cause problem?

You don't need an output capacitor connected to an input capacitor in series when just a single capacitor will be fine. If the DC voltages are nearly the same then use a non-polarized capacitor to make sure that resistor tolerances don't add up to make the polarity backwards on a polarized capacitor.

 

[whiz115]

i think most audio devices that accept input have coupling capacitors
that is happening because manufacturers don't know if the device you intent to connect already has. In case both devices have polarized capacitors what is happening? no signal? or explosion?

i have an audio device with 10uF polarized capacitors for input (it's for microphone) and 10uF also polarised for output what is it going to happen if i loopback connect it?

I thank thee!

 

[Sceadwian]

Signal lines are usually AC coupled, but aren't most speaker outputs, at least on anything even halfway decent DC coupled?

 

[audioguru]

You can connect the output coupling capacitor of one circuit to the input coupling capacitor of another circuit without any problems. The capacitors will not have reversed polarity.
Non-polar electrolytic capacitors are made by connecting two polarized capacitors back-to-back.

Most modern audio amplifiers don't have a capacitor at the output . They have dual-polarity power supplies and the outputs are DC-coupled to the speaker.