Speaker cable gauge and amplifier power

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.
.

I agree with Albertporter, your ears are the best instrument.

I just replaced the small Nordost SPM speaker cable driving my subs with big (8 AWG) cables and heard a big difference...

Thanks for those responses. Jeffreybehr, in particular, addressed my question helpfully.

I certainly agree that the best way to pick a cable is to audition it in your system. I just thought I might be able to limit the number of choices based on this set of factors.

As Albertporter stated, from a current carrying viewpoint all speaker wire size is overkill. I must admit that I have gone along with the heavy wire idea, although I have not used any of the specialized speaker cables with exotic construction.

Recently I tested some Nordist flat cables vs zip cord, and had to admit there was a very obvious difference. My plan of action is not to purchase $6000 worth of wire, but rather to purchase fan-free monoblock amps that I can loctate just inches behind my MG1.6 speakers.