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In Reply to: RE: Instantaneous current demand and wire gauge? posted by Tweaker456 on March 05, 2016 at 13:27:56
Check out the link below-
otherwise-The ability of a given wire to accommodate a given amperage is well characterized and appears as part of the IEC - and is usually given in tables where you have Volt amps on one side, wire gauge across the top and in the columns are listed the acceptable distances -
while this is not exactly what you asked - it does address the subject-the speed of transmission is a constant- through the wire and is only affected by the connections and the supply
Typically in HiFi we are in the under 1000 V/A range - so at 120 VAC the current would be 8.334 Amps - so anything over #14 wire is good for 50 feet with negligible losses - and if you use wire better than #10 you are good to 100+ feet-
Given that many of the speaker wires commonly used are bigger - the ampacity is not really an issue - it becomes the exotic construction etc...
Happy Listening
Edits: 03/09/16Follow Ups:
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.
https://en.wikipedia.org/wiki/Electrical_characteristics_of_dynamic_loudspeakers
BINGO on noting PF.
Too much is never enough
I tend to doubt all of those equations are applicable since I have heard 54 ga. Speaker Cable as I mentioned in my other post and it sounds EXTREMELY GOOD. Plus I seem to recall measuring more like 2 amps at the speaker terminals when music was playing. Could my memory be on the fade?
yes, defective memory MIGHT be in play here.
2 amps @ 54ga wire? Might get away with that at a 10% duty cycle.
Too much is never enough
It was interconnects. Ooopsy daisy.
Not 54AWG speaker cable any more Sir Geoff. Ya sure?? Ooopsy daisy?
" And it's a hard rain's a-gonna fall" Robert Allen Zimmerman
So much for the Memory, eh? You've got CRS.
Too much is never enough
I was close, zippy. Very close.
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