Sound of 777ES during break in?

I bought my 777ES about 4 weeks ago. The system is as follows: 777ES -> AQ Lapis III 1m -> Audible Illusions M3-A latest version -> Silver Audio Hyacinth 3m -> Bel Canto EVo 200.2 (monos) -> AQ Sterling II 6' -> Sonus Faber Grand Piano HOME (latest version).

For the first 90 hours the sound was excellent on both red book CD and SACD. I played mostly red book CD. At 90 hours the sound became bright, edgy and sibilant. I now have 240 hours of burn in on it in red book CD. It is still bright and sibilant.

Is this brightness and sibilance the sound that the 777ES takes on during this bad period of the break in people talk about, or should I be looking for some other source?

Thanks in advance for any comments.
Are you hearing this brightness and sibilance on SACDs also?
I am hearing this with SACD too but to a much lesser degree. I only have about 10 hours on SACD. I have the Sony and Telarc sampler CD that came with the 777ES and the Miles Davis Kind of Blue and Sketches of Spain. All of the instrumentals sound great, but the one sampler on the Telarc disk that has a vocal on it, the vocals are sibilant.
Upgrade the cheap supplied power cord.
Give it another 500-600 hours, no more than 4 hours at a time. At least that's what my friend who has one tells me.
Break in is about 400 hours. It doesn't matter how long the stretch of listening time is.

Thanks to all who have responded. I will sit out the break in period of 40 hours. On red book CD I am doing this for the most part by playing the 777ES into the Audible Illusions while the AI is in mute with the volume controls set to nothing, and the tubes are either in stand-by mode or just left one. I am putting on about 20 hours a day this way. I am now at 260.

Thanks again and I will report back with my observations at 400 hours.