newbee -- first let me answer your specific question: no there's probably not going to be much difference between a 1.5 and say even a 6.5 meter cord of identical construction. As you get longer than twenty feet though, there IS going to be voltage drop, so if one can go up by a wire size, that's a good thing.
What I meant was, that ALL amps should use 10AWG (even if they're not that high powered) because the name of the game with amps (and apparently DACs for some reason) is energy TRANSFER. This is what Jim Aud of Purist has always emphasized, and why his PCs are among the best sounding.
His Dominus PC is an effective 9AWG and I think PS Audio even makes a 6 or an 8 AWG PC! And this ALWAYS raises the question we've heard a million times: "what's the point of using a PC that has bigger conductors than the ones in your wall?"
The answer is that they do different things. The wall wiring is like a resevoir of AC. The hot conductor is just sitting there cycling from plus to minus looking for a ground. It's sort of like a big river flowing past your outlet, and all of a sudden, you stick a power cord on it or in it (like a water wheel) to get some of this flowing energy. Now, there's lots of potential energy stored in those wall conductors, even if they're not that big, because they have the reserve (inertia) provided by the entire wiring system. So if you can stick a big enough pipe into the stream, you can use it and return it back to the stream (complete the circuit) without any bottlenecks.
I guess what I'm trying to say is that the large conductors of a PC have a different function than the size of the wire in the wall. The wires in the wall just have to carry their assigned amperage without getting hot and burning down the house. The PC has to grab that energy, use it (spin the water wheel) and return it to the river without any traffic jams.
Even a lower powered amp has constantly fluctuating energy requirements, every microsecond, so it's important that it can get exactly what it requires and then return the power to ground without encountering resistance, AC intermodulation distortion (a big problem with small conductors on med to hi powered equipment), inductance and other impediments that build up in smaller conductors.
Again, with PCs, if "quick and clean" energy transfer is accomplished, power handling capacity is pretty much automatically taken care of.
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