I use "hospital grade" receptacles for my audio equipment. Hospitals are always plugging and unplugging equipment at patient beds. Ordinary household receptacles are not meant for this type of abuse, the receptacle blades lose their "spring" in no time at all. The electrical industry came up with extra heavy duty/sprung receptacle blades, tested with pull out weight tension, for the hospital industry. This construction is also beneficial to audio equipment, assuring a good solid connection. I use "20 amp" receptacles regardless of whether the receptacle is on a 15 or 20 amp circuit, as I would expect the 20 amp receptacles to have more copper and offer a better connection. There is a limit to what can be achieved by a receptacle and a good tight connection is about all that is reasonable to pay for, so I don't buy "audio grade" receptacles.