Speaker cable gauge and amplifier power

It's more complicated than that. If one only considers wire gauge in relationship to output power, all the larger speaker cables are overkill.

Here is a chart:

http://www.powerstream.com/Wire_Size.htm

Scroll down and see that 21 gauge will handle 1.2 amps of current. 21 gauge is about the size of doorbell wire.

Rather than trying to decipher this scientifically, listening with various speaker cables will provide a wealth of knowledge. I think you will find the design, insulation, RF rejection and terminations all play an equal role in the music, not just the wire gauge.

I don't have a scientific answer but when I had dedicated circuits put in the electrician said that 15 amp capable power lines were massive overkill. I was asking for twenty, he said if you pull over 7-8 amps that would be remarkable. And I use 400wpc SS monoblocs that are fairly high current on separate lines of course. That being said I have seen ads that say you should have 20 amp capabitlity for some really monster amps which I can't afford. So I settled for extra 15 amp lines instead of fewer 20s. I have never had any obvious problems.

"Using a larger cable gauge or bi-wiring will increase the amount of current required from the amplifier."

The word that has you pointed in the wrong direction is 'required'. That's not the way amplifiers work. The drive Voltage creates a 'pressure' in the conductor; the amount of current that flows is simply the inverse of the resistance that Voltage 'sees'. If the resistance is low, high current flows, generating lots of power. If the resistance is high, low current flows, generating a small amount of power. The amp doesn't 'work harder' in either situation.

In an audio situation, the load resistance--the speaker--is relatively constant*, and what varies hugely is the Voltage presented to the amp by the upstream component, usually some form of preamplifier. If one part of the signal is 20 times higher in Voltage than some other, 20 times as much Voltage will flow into the speaker.

What will change with different gages of conductors is how much of that amplifier power will be absorbed by the speaker cable, because the cable always has some, however small, resistance. Current flowing thru a conductor that has resistance, and they all do, is converted into heat. That's just one reason** we try to keep the resistance of speakercable as low as reasonable possible.

Albert's last statement is correct--there are MANY factors that influence the sound of speakercable. The thickness of the conductors is just one.

* Folks, I don't need any reminders about impedance v. resistance, just go with the flow of my highly simplified example, pls. :-)
** Another reason is so that we reduce the amplifier's damping factor as little as possible.
.