When a power cord could obviously affect SQ

@bruce19 many directly heated triode designs run AC to the cathode - straight from the transformer.

@retiredaudioguy that’s interesting, are there any that you know of that might have a schematic posted online. I have built 4 tube anmps nowv and I just don’t see how that works. Unless we are possibly miscommunicating. There is AC going to the cathode in the form of the signal super imposed on the DC current but that is coming from the signal path, not the power transformer.

Power cables make no objective difference in the sound of a stereo but, as pointed out, they provide a lot of profit for the companies who make them. Same with interconnects, digital cables, etc.

@bruce19 cannot find a a schematic but:

on a 300B pins 1 and 4 are connected to the 5V AC of the transformer.  A pair of 50 ohm resistors are in series from 1 to 4.  The center tap is then connected to the main cathode bias resistor and its bypass cap to ground.  

@retiredaudioguy 

I see the Triode Wire Labs IEC’s he uses are Furutech Gold. Not sure if you already have done this in your system or not yet, but you should get the Furutech Gold outlet to match in order to be better able to tell the differences between power cords, and for better sound overall of course. 

And believe it or not, my experiences are all components, and I include cables and receptacles in the heading of components, need 200+ hours to stabilize so even if you don’t believe this, do it anyway before arriving at any conclusions. If it was the rhodium Furutech outlet more like 300-400 hours. Seriously. 

https://furutech.com/product-category/receptacles/

And for my 2a3, which of course is an oddball build and quite different to yours, I find the driver tube, a single 6dj8 in my case, makes more of a sonic difference than the output tubes. For 2a3’s I currently have RCA’s, Black Treasures and I am trying a set of JJ’s as of last week. (The JJ’s are not working at the moment, discussions with the retailer ongoing). If I was going to spend big bucks for a new set of 2a3’s it would probably be Emission Labs mesh plates. 5 year warranty is unbeatable. Takatsuki’s I can’t justify currently, knowing there are a dozen other things I could change in my system (like power cord on the amp) that would change the sound more for half the cost. 

Congratulations on the new amps!