Hi Marty:
I was running an Audion Silver Night 300B stereo amp @ the time and started to loose midrange forwardness and clarity. HF's also became harsher during this period and I was using a Bel Canto DAC 1.0 DAC (one of the smoothest around 1.5 years ago).
The Leviton was the first replacement outlet that I had tried (the old one was water damaged) and it ended up being the last thing that I checked in regard to the change in sound. I replaced it with an inexpensive P&S 5252 which brought the familar sound of the setp back. Replacing the other outlet with a 5252 (in the same line from the breaker box before the audio outlet) improved the sound even more. I suppose that if the line runs through a light switch (prior to the audio outlet) that this should be checked and/or upgraded as well. I do not have dedicated lines.
Oddly enough the Leviton sounded better when first installed and then gradually went down hill. I had first thought it to be defective in some way when I finally replaced it, but found a few comments from people over @ AA who had the same experience.
The outlet is now installed in our neighbor's garage @ his work bench. It still has a very tight grip and I don't have a clue as to why the sound changed so much.
I have a Hart and Hubbel outlets, but have not gotten around to trying them out yet. I may retro fit them into one of my power conditioners when I muster up the nerve.