Power cords: does length matter?

@pennfootball71 Shouldn’t generalize based on limited exposure. The standard length of SR cables is indeed 1.75 meters, but custom versions of certain models like the Venom HC v2 can be made in any desired length with various connectors. The "standard" length may indeed be set based on market demand rather than technical considerations discussed. I have not seen any technical white paper published by Shunyata Research to support such claims a 1.75m or length around it being an optimal design. Additionally, I have seen some audiophiles claim that power cables need capacitance, which is not accurate. In reality, high capacitance in high voltage applications can lead to power loss and inefficient operation of devices.

I’ve heard girth is more important 

@brian8383  , I believe that 10AWG has already been settled upon.

It sounds like the power supply in the components grab power about 2m away from the component. I don’t mean it is using the power 6.6’ away just that it is the length that matters to the sound. Nordost does recommend 2m. Is that to sell more cable or is that the minimum length they sell to keep things tight. I have not tested this but it’s so interesting. What I have tested is different power cords on the same pieces of equipment. That is awesome that power cords do not make a difference on some of your systems and you are happy with the sound. Seriously, you are lucky. That being said I did do a sound test using different power cords like Nordost Blue Heaven, Puritan Classic Plus and Ultra XX, Straightwire Pro Thunder and Black Thunder, and three different ESP power cords, even some Audio Quest NRG. They all sound different on every component I tried. I even bought an EIC to C7 (figure8) adapter to test on the Blue Sound NODE. Every power cord had a different sound in one way or another. Detail, Decay, Midrange, Bass, harshness. One thing I was surprised about how one power cable might not sound good with a different brand on a different component. In the end it all can make a difference. I have a killer Kubala Sosna Elation on my ARC Ref 5 SE preamp. I do not want to spend another $3k on every power cord so I am looking for a power cord for the amp and DAC to keep the killer sound. 

@immatthewj       The really short answer to why most stock power cords are similar is that the cord is seldom the reason for purchase.  Many customers don’t know enough to care, and the rest will buy what they want and don’t want to pay much for what gets tossed. 

@lanx0003    I believe you have arrived at the same conclusion as millions of marketing managers over the years – the optimum design (length, in this case) is the one that sells the best.  Is this purchasing preference based on what customers feel sounds the best (how many buy a handful of lengths of the same item so they can compare?)  vs how many buy what they think will be “about the right type and length” to get from wall socket to device?   We leave out for now the issue of price point, since every customer has a different idea of what is a “good value” for them at any particular moment.  

@tattooedtrackman
          It sounds like your experience when comparing two very similar cables seems reasonable.  There is minimal difference in the amount of shielding, conductor length and probably location of the power cable throughout its length in the room vs. other electrical devices, ground planes, adjacent or crossing cables (at right angles, of course…)  etc. that might have an impact on the electromagnetic environment the cable will be interacting with. 
Given the same brand and performance level of cables, the effects of differing or worn terminations can probably be excluded, and the comparative ages minimizes the impact of minor design changes, insulation degradation through aging of the plastic dielectric, or breaks in the shielding due to frequent flexing of the relatively fragile metal mesh usually used. Heck, given the subtlety of the effects being looked at here, even someone accosting a cable with the nose of a vacuum cleaner could cause an indentation in the shielding or insulation that would slightly change the impedance of the cable at that point, possibly causing an electromagnetic reflection up and down the cable forever after.  

@jlbkmb1958  re: “Seems like just adjusting the tube bias based on whatever voltage you end up with is the easy answer. The line power goes through an input transformer and a rectifier before it’s actually used. I assume solid state amps do something analogous?”  

Similar, but in opposite ways.  Tube units need to INcrease voltages for the tubes, and unless really well pre-filtered, thus INcrease the interference signal voltage.  Semiconductor devices work at low voltages, so their power supplies generally DEcrease the voltages sent to the circuit boards, thus DEcreasing the amplitude of the interference signals as well.  That does NOT mean they go away, and interference noise will be re-amplified in any gain stage in the device.  In either case, good designs work to isolate the power and signal sections of components and filter the dickens out of the PSU’s output. 

To these and others above, one consideration affecting power cables, at least in the USA, is that building codes commonly state that residential wall outlets cannot be more than 8’ apart, so a 2-meter cord can almost always reach to one, and most first-time cord buyers will be mad if the recommended cord does not conveniently reach the outlet. If I were buying a power cord and I had to choose a length without being able to audition it/them first I'd probably be far more concerned about the path it has to take to get to a dedicated outlet than the overall length. 2 meters MAY be an optimum length, but often for reasons other than actual length.

That said, when I am at the point where cable effects are my top concern, I would want to have evaluated ALL the potential interactions between the active devices in the system, including microphonics affecting the stylus and tube grids, radiated electromagnetic interference from devices locally and in adjoining rooms, be they laterally adjacent as well as above or below, and even the proximity of wireless IOT devices which can, through the interaction between their signal and that of other devices on the network, cause higher and lower harmonics that can couple to sub-optimally shielded points within ANY nearby cabling, and cause issues.  Effects can range from dropped packets in the data stream to your audio streamer (which SHOULD be auto-corrected) to just inducing something that sounds “a bit off”, and that is what we are at the level of here.  [As others noted, also try to keep IOT on 2.4 and audio on the 5gHz channels and suggest the same to your neighbors unless they are far enough away that their weaker 5gHz signals can’t reach to your place.]

Bottom LINE:  Power Cords, like everything else, exist in a complex environment.  The effect on each individuals' perception of the resultant sound will be impacted by both the design of the particular cord and the way it interacts with surrounding elements – electronic, magnetic, environmental and spatial.  Finding the optimal result is as much art as science.  Everyone’s mileage will vary, often from room to room in the same home and even the humidity that day. Enjoy the ride! 
-------------------------------------------  
Full disclosure- my background and signal interference in general:  My days of having the luxury of optimizing my space for my audio system are past.  Although an Electrical Engineer, I have also designed and built both residential and commercial buildings, including my own home.  I made sure that home had buried utilities, excellent service entrance grounding, whole house surge protection on both phases, 5 subpanels with oversized feeds from the main panel, and a separate transfer panel for the underground feed from the generator out back. When the Verizon guys I was training gave me a carton of 1000’ spools of coax to wire the place I came back for more.  When moving out of that 5000+ sf suburban home a few years back, we chose our new apartment based on the concrete and steel construction between each tenant and felt having a hardware cloth-like steel mesh that the 100+ year old ceiling plaster is embedded in was a big plus. I know this reduces some top or bottom interference, and foot-thick concrete walls all around certainly help, but I still get, as of this writing on a Sunday afternoon, 15 wireless networks from where I sit to type.  My network analyzer says I have good quality signals from the top 8 of them. The ceiling mesh is way too coarse to effectively block signals at cellphone or Wi-Fi frequencies.  Look at the size of the holes in your microwave oven door to see what is needed to block LOW-band cell signals and Wi-Fi.
Your personal situation may be less challenging, but I have visited and tested some locations where I see close to 40 viable sources of RF interference, all trying to share the same limited spectrum, and each one boosting their power to get their set of data packets through all that hash. OTOH, our ASUS Zen XT8 4-node mesh network throughput was cut from 1 GB/sec as transmitted to 10 MB/sec throughput between our apartment and our daughters’ unit, one floor above and about 20 feet away.  Only good for Minecraft despite focusing the antenna radiation pattern at both ends! Lesser units totally failed after 1 wall. 
 If I were to add in the kitchen appliances and potential interference from the surrounding spaces in a volume equivalent to the average private home, I’d have over 40 SETS of surge and RF sources including air conditioner compressors, refrigerators, microwave ovens, etc.  
At least even this is better than one place I lived (I think I mentioned this in an earlier post) where a local AM radio station was literally in my back yard, and I had to leave my system on all the time, because if the solid state amp was turned off, and even if it was unplugged from the wall and any input, would still play whatever was coming from that station.  The output transistors were acting as detector diodes, and the whole amp was effectively a very expensive crystal radio set. I pitied any cats whose whiskers touched unpainted metal.
 

Benjamin Franklin was once asked how long a man's legs should be. His answer was simple: "Long enough to do the job." Unsatisfied, the questioner continued, "And how long is that? Franklin replied, "Long enough to reach the ground." The questioner continued, "What then his manhood?" Not missing a beat, Franklin replied, "The same."

Similarly, I think that holds true for power cables. They should long enough to reach the outlet. And from there, the electrical wiring should be long enough to reach the power generators. As for how that cabling should be configured, I leave that to you and your power company to work out.