When a power cord could obviously affect SQ

@richardbrand I’ve quoted your entire post because it should be mandatory reading!  You have provided direct evidence for the theory that it is EMI coming from your component that could make a difference. 

Indeed, managing internal noise generated the audio component itself is the primary concern, not preventing external noise from the ether infiltrating the power cable. That a component that is most sensitive to noise can at the same time be the most significant contributor of noise (i.e. self-contaminating) is perhaps ironic, but true. 

We can bear witness here to those who view a better power cable as some sort of power conditioner, and this is a common misconception. It’s easy to make a power cable that rejects internal high frequency noise (and some cable sellers evidently do). The problem with that is reflecting internal noise back toward the source is going in the wrong direction for the aforementioned reasons. 

@retiredaudioguy  @invalid @erik_squires 

As you say Erik, live and learn, thanks for that Invalid you are absolutely correct! So the heater and the cathode are one and the same on all 2A3s. I was able to find this schematic for a Sun Valley amp and, realizing that this may not reflect the situation on the amp in question but assuming it also possibly may, it looks like that current to the amp/cathode comes after the rectifier and so is DC. If it were AC wouldn't you expect to hear a hum at whatever frequency the AC cycle is?

I still feel that any problems of this sort would need to be thoroughly addressed in the circuit and not left to the choice of a power cord.

@bruce19 hum is avoided by the cathode resistor being attached to the mid point of the resistors across the filament.  In this circuit there is a trip pot that can be adjusted to minimize any hum or noise.

I guess one might add ferrite rings on the filament leads and a small bypass cap (.001 mf) across them to get rid of any RF crap.

If you google "filamentary triode" there is a good discussion.

OP

Good luck and please post your observations.  

I have the 845 powered Audio note clone. I tried a few choices from audio quest to transparent. for me I prefer the sound of the Shunyata Theta

My first experience with all the black magic coming true right before my eyes, the first time I bought an upgraded cable for any of my components (I’m a professional cable splicer, outside-plant copper cable splicer). My company based in Silicon Valley, most of my work is in San Francisco and the Bay Area. So I know a little about cables…. I was always skeptical. I thought it, obscenely nefarious and predatory marketing, claiming an AC power cable could improve your sound in a stereo. But one day I bought a NRG Z3 from audioquest. A “perfect surface”, long grain copper 3 conductor, 14 awg copper AC power cable. Came home and I was between reference stereo systems at the time, had just moved and all I had was a pair of KEF Q3 meta bookshelves and my AV receiver for the home theater, Onkyo TX-NR7100 integrated amp. The first thing I noticed, within 10 seconds of play time at LOW TO MEDIUM volume, was just plain more MEAT on the bones, I cannot describe it any other way, a little tiny increase in sound stage, the width, and depth I was perceiving the sound coming from. But the sound mainly got “thicker”, meat on the bones is what I can honestly say. Worth the $400 bucks, entirely. 
Now, I’m sold on AQ cables, but upon hours and hours of further research, looking to upgrade to LessLoss power cables or Analysis Plus. 
 

would anyone like to buy, 5 Audioquest NRG Z3 and Monsoon power cables, 1 & 2 meter, 18 month old