What was the first power cable that you noticed a difference in the sound?

It was the Shunyata Delta NR. Frankly, I was shocked over how a cable could make that much of a difference. But I did not like all of the changes (enhanced mids but at the cost of toning down the highs, i.e. less bright), but changing the fuse to a Rhodium fuse and then again to a Synergistic Purple fuse addressed that! 

@dcpillai 

Hi there, Please tell me about your system and that the Delta NR was plugged into.

Oh and tell me more about the Rhodium fuse, I must admit I have never heard of that.

 Thanks.

@sudnh ,

 I have a Hegel H390 going to KEF Reference 5 speakers by way of either AQ Rocket 88 cables or Audio Art’s Statement E cables with the lockable Rhodium bananas.

I never expected power cords made a difference. Then I got a used 2M Audio Art Power I Classic cable, used with a big class D amp. Immediately heard subtle but worthwhile differences. Got a 2nd one of these (1.5M) and put it on a tubed headphone amp. Heard a slight but worthwhile difference.

These are budget cables, bottom of the line in Audio Arts lineup, but they made a positive difference for me.

@curiousjim "I have bought six or seven different power cords, none over $500 and have noticed little or no change in the sound of my system"

correct! good quality equipment must supply sufficient power cable, some brands like Esoteric have “upgraded” power cable option available for extra charge. 

if someone can “hear” sound improvement after replacing power cable, before claiming power cable problem I would in details, for example what cable was replaced, outlet degradation issues etc. In many cases de-ox spray fixes contact issues, w/o changing need to replace cable.