[strojo]

 
This is the receptacle on the back of my AV receiver.  If I'm getting a replacement cable, does it matter if I get one that has the three slots and ground pin on it even though the receiver doesn't utilize it?
 
Thanks!

 

[plasmatic-d]

Hi Strojo,
to quote Wikipedia: "Occasionally, plug and socket combinations may allow power to flow but may not meet product standards for mating force, earthing, current capacity, life expectancy, or safety. Improvised or user-modified connectors will not meet the product safety standards. Adaptors between different standards can overcome mechanical incompatibility."  
 
Judging by your picture, you're talking about a single-phase without safety ground connection.  That third center pin if it had been required by your receiver would have been your earth ground (in North America anyway).     If your receiver socket *did* have the third pin, you'd want to assure it was suitably earth grounded for safety (PC's, some televisions, etc. have this).   But it doesn't.   
 
(on a receiver, and most AC powered audio equipment, that earth ground if it had been present could have caused some unwanted noise, as in ground loops)
 
Since yours does not "want" that connection, and if you've got on hand a 3-wire power cable that will fit, IMHO it should bring no harm to have 3rd pin on your cable's plug go unused.   
 
I have that situation on my subwoofers here.  The sub has a two pin socket (just like your picture) and my cable has 3, electrically the sub works, but it's a loose fit with the power cable.  For my purposes, I have not obtained the "proper" power cable with just 2 connectors (bought sub used, it came with a 3-pin plug on the cable).   I recently purchased a second, identical sub (SVS PB13 Ultra) new from the manufacturer, and it also came with a 2-pin socket, and a 3-pin cable plug!  So, there's some anecdotal validation FWIW.
 
A couple of times the sub has quit working, it's because that cable has come loose with vibration to the point where it's no longer powering.  I've tried a number of cables, they all seem loose even new ones.  So, "mating force" up there on the Wiki kinda means that too, I suppose.  Maybe a good popsicle stick stuck in there alongside might help!  Good luck!

 

[strojo]

Thank you!

 

[plasmatic-d]

Hi strojo,
 
I was curious so did some digging.  The actual 2-pin cable end connector is apparently more common in Europe, but the cable end is included in a national standard in USA called "IEC 60320 C17"   (socket is the C18)
 
Many places on internet that sell cables like this are wholesale, "call us for quote" kinda places, like in quantity 10,000 or something.  Not what we need.
 
However, I found a couple of individual cables for sale on Amazon FYI - As before, the 3-slot cable end will work, we can continue to use;  and the national standard intended it to be usable in the 2-pin IEC socket, but in my case it's loose there  (probably because of the vibrations...). So, here's one:
 
https://www.amazon.com/HQRP-KDL-52XBR9-KDL-52Z5100-KDL-55EX500-KDL-55EX501/dp/B00RZDLIRE/ref=pd_lpo_328_lp_t_3?_encoding=UTF8&psc=1&refRID=SW3D0DFQN8JPHYA90PKN
 
or a right-angle one, here. This one would let me place the Sub closer to the wall behind:
 
https://www.amazon.com/Conntek-29343-072-NEMA-1-15P-Angle/dp/B00ZFO5JR0/ref=sr_1_fkmr0_1?srs=2529582011&ie=UTF8&qid=1490037406&sr=8-1-fkmr0&keywords=c17+right+angle
 
after shipping, they're roughly the same price (if Prime).  I'm not sure this fix is worth the $ to me, considering what I have does work (usually), but I thought I'd share!
-d.