Ah, that explains a lot.
I've been only dealing with DC circuits until now. I have yet to play with
audio or AC, I've only been playing with micro-processors and supporting
components.
Robert
:)
> -----Message d'origine-----
> De : Homebrew_PCBs@yahoogroups.com
> [mailto:Homebrew_PCBs@yahoogroups.com] De la part de Henrik Olsson
> Envoyé : avril 26 2006 13:13
> À : Homebrew_PCBs@yahoogroups.com
> Objet : Re: [Homebrew_PCBs] Re: Some toner transfer experiments
>
>
> Robert,
> Depending a bit on what you are doing they may be "the same"
> - or not. Impedance is sort of resistance but it varies
> depending on the frequency of
> the current passing thru it.
>
> For example, take your average speaker, it will probably have
> a label on it
> saying Impedance 4-8ohm but if you take your meter and measure the
> resistance of the coil it will be near zero ohm.
>
> A high power amp can easliy destroy a speaker if the output
> is offset from
> 0V. That's why audio amplifiers have a protection circuit on
> the output that
> disconects the speaker if there's any DC-component at the
> output. Before
> push-pull circuits made it's way into the amps they used to
> have a big
> capcitor in series with the output to make the output
> centered around 0V
> instead of 50% of the powersupply voltage.
>
> See, there you go, that cap has a VERY high resistance (DC)
> but it still
> passes current from the amp to the speaker (AC).
>
> HTH
>
> /Henrik Olsson.
>