Originally Posted by
Barabaika
Doesn't Dura Ace need electrical cables?
No, but Dura-Ace and Ultegra
Di2 do.
Originally Posted by
Barabaika
I recommend the ones that are made of pure silver with gold contacts, they should shift better.
So long as the signal gets successfully transmitted to the derailleur, it'll shift exactly the same regardless of whether the wire is silver or copper. Not that you have a choice anyway, since Shimano doesn't sell Di2 e-tube wires in different configurations; just different lengths.
(Some people claim to hear a difference between silver and copper wire on analog circuits like speakers. I don't buy it. Neither does my oscilloscope. And it makes literally zero difference in a digital circuit where the signal is binary. Ones and zeroes are ones and zeroes, regardless of the transmission medium.)