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Technical and scientific discussion of amps, cables and other topics.

RE: Instantaneous current demand and wire gauge?

For power cords: Audio gear has power supplies, typically with transformers, rectifiers and capacitors (and sometimes, regulators).

You can't just apply ohms law to work out the instantaneous current for several reasons.

1) The power supply takes current in small bites. Sometimes current is only flowing for a small percentage of the cycle. This is because of the caps and rectifiers - the rectifiers only conduct when the voltage from the transformer is higher than the voltage in the reservoir caps.

2) Usually the power supply will present a complex load, ie it's inductive. So current and voltage are not in phase. Leading to ..

3) Power factor. (look it up..)

For speaker cables : speakers are also typically complex - inductive (unless they are capacitative ;). But also a speaker has moving mass, and for example, when you get a pulse (or the music stops suddenly) the speaker keeps moving and acts as a generator, pushing current back into the amp. And if the amp has a very low output impedance, you have a generator looking into almost a short circuit, so you can get pretty high instantaneous currents.

Long and short of it - ohms law doesn't apply here either.

This is basic electronics, nothing controversial.

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