Recommendations for 20 amp electrical outlets

My view is that there are two main considerations about receptacles (also includes cord plugs and IEC connectors).

First, what is the base metal used for the product. There is basic brass that is the norm for commercial products, Hubbell, etc. The most basic form of brass is about 1/3 zinc and 2/3 "regular" copper. Next is Phosphor Bronze that is found in products from the companies that offer audiophile caliber receptacles and cord ends. Phosphor Bronze is a high copper content form of brass. Next is "pure copper". Well, there's more than one kind of "pure copper". Beryllium copper seems to be the top dog for receptacles and cord plugs.

Second, what is the plating? Nickel, gold, silver, rhodium, platinum, palladium or some combination or no plating at all. Each has it's own sound character. 

Since everyone has their own perceptions and preferences, you have to hear these different products first hand. While my preference is for un-plated receptacles and cord ends most of the time (I do have several Oyaide 004 cord ends on several power cords), many audiophiles like the sound of the various plated choices that are available.

For me, un-plated brass and plated brass are non-starters. The more copper and the better the copper is, the better the sound. The outlier here is the Maestro outlet. I seems to be some form of brass but, does not sound like a typical brass receptacle.

I use two different receptacles at the same time. My main system has two dedicated power lines with a two gang box on each line. Each box has two receptacles. Each box has one Maestro receptacle and one Oyaide R0 (not the R1). The R0 is an un-plated beryllium copper outlet (grips tightly). This allows me to tailor the system's sound more than I could using just one particular outlet only. The Maestro is somewhat brighter and a little more open sounding.

I choose, primarily, to use un-plated connectors since I am extremely sensitive to high frequency problems such as brightness, brashness, harshness, etc., etc. In addition, to my ear the system is more relaxed sounding than it would be otherwise.

I met Galen Carol (Shunyata) at the 2018 AXPONA and he told me a couple interesting things about outlets.

1. He recommended Hubbel 5362 outlets. He said they will perform as well or better than any exotic outlets.
2. He didn't recommend hospital grade outlets because they are built to withstand chemical corrosion as their first priority. They have stainless contacts which do not conduct electricity as well as copper.

I'm building a new house with an audio room and I will be using Hubbel 5362's for the three dedicated 20 amp circuits. However, I will have to install them after the electrical inspection because they are not tamper proof as @pcolvin mentioned.

@8th-note Buy some 20 amp tamper proof Levitons from Home Depot.  They're under $5 each. Then save them for a rainy day once you swap them out.

Per my dealer, I avoided the Furutech fancy outlets.  I have a total of six dedicated 10a circuits with 10 gauge wires (two systems).  I have a pair of Shunyata's and four PS Audio.  I can not hear a difference.  They both grip well, although I have made wall plates with semi circular supports under the bottom outlet to support my heavy cords, and they work wonders.

I replaced my circuit box and then ran 12 gauge to the HiFi.  Interesting, every box I looked at used aluminum for the breakers and hence, aluminum to copper wire. So I don’t understand all the debate over which outlet is used. From the source, we probably all have a problem with connecting aluminum to copper.  No outlet, no matter how sophisticated in materials science, will alleviate this problem.  I just needed a very good outlet to make a very tight connection and then let the DC filter and line conditioner cleanup the mess.  So far, very good .